Concerned that International Business Machines Corp. and the government were about to destroy vital documents and evidence collected during the Justice Department's 13-year antitrust suit against IBM, a federal judge refused today to allow either side to begin returning documents to their owners.

In a 20-minute hearing held exactly one month after the landmark suit was dropped by the Reagan administration, U.S. District Court Judge David N. Edelstein said that even though the suit was dismissed, it is essential that the case record developed during the 7-year trial remain intact.

"A trial is a public event. What transpires in the courtroom is public property," Edelstein said, adding, "It is especially important for cases of historic significance that the record remain intact."

As a result, Edelstein said he would not sign an order requested by IBM and the Justice Department on the day the suit was dismissed that would have lifted earlier court rulings to allow both sides to clean out their massive files and return all collected documents to the proper owners. Many documents came from other companies; hundreds of others under court protective orders involve IBM trade secrets or classified government documents about data-processing.

IBM and the government referred to the requested order as "routine housekeeping." But Edelstein said he had received "numerous inquiries" about whether the order amounted to a "destruction of the record."

Although the judge pointed out that he was not charging either side with collusion, he said IBM and the Justice Department had an obligation to give the court a detailed inventory of the documents they wanted to return.

However, lawyers for both sides said such a requirement would be impossible, given the large number of documents that had been accumulated.

"There are perhaps tens of millions of documents scattered throughout government warehouses" and IBM facilities, said Thomas Barry, IBM's lead counsel. Because they were under court orders to keep any document having to do with data-processing--even though these documents may have been irrelevant to the suit--millions of documents have not been catalogued and have been lumped together in giant batches labeled "otherwise disposable."

To make an inventory of these documents would be "a mammoth undertaking that would take months and months," Barr said.

What's more, the documents "have all been in the public reading room for the past six years, and damned few people" have come to read them, Barr told reporters after the hearing.