A medical inflation/deflation drive device comprises: pressure generation means (11, 12, 40) which, in order to repeat the inflation and deflation of a driven device (22), alternately applies positive pressure and negative pressure to a piping system (18) communicating with the driven device (22)； a gas tank (71) which, according to the difference between the pressure in the piping system (18) and the pressure in the gas tank (71), sucks a part of gas within the piping system (18) or discharges a part of the gas within the gas tank (71) to the piping system (18)； a valve means (72) for selectively opening and closing the connection between the gas tank (71) and the piping system (18) ； and a control means for controlling the valve means (72) in such a manner that the valve means (72) is opened after a predetermined period of time after the time point at which the application of the pressure by the pressure generation means (11, 12, 40) is switched from the application of the positive pressure or the negative pressure to the application of the negative pressure or the positive pressure, and that the valve means (72) is closed before the next switching.
