PURPOSE: To provide a brake control actuator or throttle control actuator for which compatibility between a performance phase of controllability and responsiveness and the cost phase of low price setting, etc., shall be attempted.

CONSTITUTION: When an actuator includes a shaft 9a and a piston 6a that make following action on the surface of a cam 8a driven by a motor 7a, and includes a cam follower 9b in a contact part between a shaft member and the cam 8a, a non- circular gear combination 7d, 7e having such a construction by which a speed reduction ratio is set high at a position where the volume on the side of a wheel cylinder 3 is minimum and set lower as the volume increases is provided between the motor and the cam 8a. At such a position where a sufficient speed reduction ratio matching a high pressure can be secured and the volume increases duly cause impossibility of pressure increase, the speed reduction ratio is reduced so as to increase the rotation of the cam 8a. The motor can be always placed in its action near the maximum output point so that required performance can be achieved under the necessary minimum performance. It is also possible to attempt size reduction of the actuator/price reduction of the motor, to reduce a motor rotational quantity when it is actuated until full pressure reduction so that cost reduction owing to improved durability the motor may also be attempted.