People in many places have been wondering what to do with their free time lately. But only France, so far as we know, has a minister of free time to look into the matter. He is Andre Henry, a long-time teacher, and perhaps no profession would be more suitable preparation for the post President Mitterrand established last year. For learning in all its varieties is the key to coping with the new age of automation and computers into which Mr. Henry is supposed to usher the French. Already he is developing an improved system of continuing education to help adults in the transition to a period of fewer or different jobs and shorter working hours.

Does one have a sense of deja vu (that's French for feeling you've been there before)? One does. It seems so long ago that every scholar, pundit, and other dispenser of free advice was warning about automation and all the awful leisure time that people were going to have and how they could learn to use it constructively and not - horrors! - the way they really wanted to. A few decades later, though, the warning voices really mean it. The rise of computers has led to brainwork being replaced as well as brawnwork. One signal: it is becoming common in Europe for workers to be paid extra benefits if they work less than the regular number of hours.

The shining promise of computers must not be lost in serf-like subservience to them. This is part of Minister of Free Time Henry's mandate. Other countries, notably Austria, have shown foresight in calculating the potential effects of technological change. But France is bidding for leadership, not only with its free-time ministry but with a whole research and technology program. This includes Paris's new World Center for Microcomputer Science and Human Resources, headed by specialists from the Massachusetts Institute of Technology.

The center already has a pilot project going in Senegal, an earnest of its intentions to spread computers, computer education, and computer job creation - in contrast with job elimination - beyond the industrial nations. Other projects are planned for the Middle East and Far East. The concept springs in part from Jean-Jacques Servan-Schreiber's argument that the developed nations will find it necessary for their own good to bring the third world along with them in this new ''industrial revolution'' - rather than speeding heedlessly ahead as in the previous industrial revolution and transferring their know-how much later.

Certainly this is a time for the widest horizons of human thought. Training has to be kept up with technology. So does the definition of what work is. So does the calculation of human and mechanical input in the measure of productivity.

There is delightful Gallic candor in speaking of ''free time.'' But it may be a little like the semantics of today's students, who so often interrupt their formal education for pursuits that may or may not also have educational value. Do they ''take a year off''? Or do they ''spend a year away''?

In the world of the future, free time will challenge each of us, not only a minister in France.