A picture caption that appeared in some editions of the Metro section yesterday incorrectly said that Rep. Frank R. Wolf (R-Va.) had made an error in reporting his campaign finances. The error was made by the staff of Rep. Stan Parris (R-Va.). CAPTION: Picture 1, Rep. Frank R. Wold . . . plans to collect $1 million; Picture 2, John G. MILLIKEN . . . fund-raising praised by democrats

Rep. Frank R. Wolf (R-Va.) has raised almost $500,000 in his reelection campaign against Arlington County Board Member John G. Milliken in what may be Virginia's most expensive political contest this fall.

Milliken, a Washington lawyer and former Democratic congressional aide, reported yesterday that he has raised $312,573 for the Nov. 4 race against Wolf, who is seeking his fourth term.

Northern Virginia's other Republican congressman, Rep. Stan Parris, who is currently unopposed, disclosed yesterday that he had raised less than previously reported by his staff. As of June 30, he had raised $293,356, instead of $400,000.

A spokesman for Parris, who long has been regarded as one of the leading fund-raisers in the Virginia congressional delegation, said he had incorrectly added funds previously raised by Parris to those he had collected this year.

Fears of Parris' large campaign treasury have scared many Democrats from challenging the congressman. Until July 2, former Alexandria mayor Charles E. Beatley was challenging Parris, but he withdrew, worried that the stress of the campaign was a risk to a recently discovered heart problem. He had raised $20,000.

Democrats praised Milliken's fund-raising yesterday. "It's an extraordinary showing this early in the game," said Mark Johnson, an aide to Rep. Tony Coelho (D-Calif.), chairman of the Democratic Congressional Campaign Committee. "Very few candidates, nonincumbents in particular, will be reporting comparable amounts."

However, Wolf spokesman Edward Newberry said he was not surprised that Milliken had been able to raise almost as much as the congressman this year. Wolf began the race with $104,000 raised last year.

"With connections to Walter Mondale Milliken's law partner , former governor Charles S. Robb and the D.C. crowd -- the lawyers" Newberry said, "we thought he would raise more."

Wolf and Parris will be getting additional help from the National Republican Congressional Committee. The committee held a fund-raising reception with President Reagan last night to collect money for 25 Republican incumbents "that need it most," according to invitations that included Wolf and Parris' names.

Wolf has spent $218,800 -- almost three times as much as Milliken -- and says he plans to collect $1 million before November; Milliken says he hopes to raise $550,000.

Almost a third of Wolf's money, which totaled $479,679 as of June 30, according to new financial reports, came from political action committees, including those representing Chrysler, General Motors, Mobil Oil and Tenneco.

Milliken received considerable financial support from labor groups, including the AFL-CIO and the International Brotherhood of Electrical Workers. In addition he received $10,000 from the National Education Association's Political Action Committee.

Wolf's district includes Arlington, Loudoun and the northern half of Fairfax county as well as Fairfax City and Falls Church.

Parris, who represents Alexandria, southern Fairfax, eastern Prince William and northern Stafford counties, may not be unopposed much longer.

Democratic officials said they expect to nominate a replacement candidate, possibly former Alexandria vice mayor Melvin L. Bergheim, before the end of the month. Beatley, Bergheim's next door neighbor and longtime friend, may serve as honorary campaign chairman.

"We don't believe in ever giving the Republicans a free ride," said George C. Rawlings, chairman of the 8th Congressional District's Democratic Party.

Parris spokesman Dick Leggitt said Parris was in excellent shape to challenge any candidate the Democrats may field.

More than $8,000 in contributions to Parris came from Northern Virginia developer John T. (Til) Hazel, his family and his business partners.