PURPOSE: To obtain a small-sized compact pressure generator easy to be operated by providing a remote-controlled motor, a speed-reduction gear, a rotational shaft, and a cylindrical slider.

CONSTITUTION: When a motor 3 is operated for rotation, the rotation of an output shaft 3c of the motor 3 is given speed reduction at three stages by planetary gear lines A, B and C, and furthermore reduced in the speed in accordance with the gear ratio between a small gear 17 and a large gear 18 to be transmitted to a rotational shaft 19, which is driven for rotation. Thereby, a slider 20 and a piston 21 are vertically moved in one body, and the capacity of a pressure chamber S3 is changed. For example, when a piston 21 is moved upward, the pressure of oil inside the pressure chamber S3 is increased, and this oil is supplied to various apparatuses, for instance, an oil pressure buffer to be used for a driving source to adjust a spring load.