The tourism business feels slighted. Agriculture has its own Cabinet department. So does housing. But the multibillion-dollar tourism business has nothing more than a miniature bureau and a mere assistant secretary.

"Grossly neglected" is the phrase used by the lobbyist for the Holiday Inns.

What they'd really like is their own agency, independent of any department. But they would settle for an undersecretary inside the Commerce Department. An undersecretary reports directly to the secretary and usually oversees a vast portion of a Cabinet department.

As it happens, the Congress is sympathetic to the tourism industry. The Senate has already passed a bill giving it an independent agency and $10 million to get started.

And today, the House will take up the issue on a slightly different bill, upgrading the current U.S. Travel Service and giving its chief undersecretary-level powers, and a salary of $60,662 -- on a par with the director of the Central Intelligence Agency.

Similar bills passed Congress last session, but were pocket-vetoed by President Carter.

The bill does have its opponents, few though they appear to be. "When we are trying to balance the budget by, just to cite one example, cutting Social Security benefits to the elderly, it is hardly in good taste for the casino, resort and hotel industry to come to Congress asking for a handout," said Rep. Patricia Schroeder (D-Colo.).

She points out that the tourism business promotes itself prodigiously without help from the government. American Express, for example, spent $62 million in 1978 on advertising, and the largest hotel chains spent $59 million on advertising in 1979.

Burt L. Talcott, lobbyist for the Holiday Inns, wrote to Schroeder in defense of the bill, pointing out that tourism is the third-largest industry in the nation, and "may be larger than agriculture."

"McDonald's may employ more persons than U.S. Steel," he wrote. "Seventy percent of Holiday Inns' guests are business-related."

A factor throwing a bit of weight on the side of tourism is that more than half the members of the House belong to the U.S. Congressional Travel and Tourism Caucus. The same is true in the Senate.

Sponsors of the House bill are so confident, in fact, that they have put the House bill on the calendar under rules that require a two-thirds vote for the House for passage.

That will send the matter to President Reagan. So far, despite its stance against subsidizing private industry, the administration has not declared itself in open opposition to the House bill, but has said only that it would prefer to move the U.S. Travel Service to the international trade section in Commerce.