To provide a costless drive device which displaces an output member of a hydraulic driving power to follow the operation input and which is excellent in operability and responsiveness and solves slipping and heating problems.

This drive device is provided with an operation input means 1, a command signal controller 5 outputting instruction signals, a motor rotating according to the instruction signals from the command signal controller 5, a respondent member 7 making a displacement in accordance with the revolution of the motor 6, and a relatively displaceable driving output member 8 against the member. And also it is provided with an oil pressure-transmission means 10 conducting the hydraulic oil from the oil-pressure supply source 9 in accordance with the relative displacement and displacing the driving output member 8 by the oil pressure. The driving output member 8 is displaced to a specified direction so as to follow the operation input to the operation input means 1.