Abstract: A side support control device for use in a vehicle seat in which by an occupant's switch operation a motor is driven to thereby control the operation of a side support so as to prevent the occupant from losing his or her sitting position. In the control device, the number of rotations of the motor to move the side support is detected by a rotation sensor, the detected number of counts is stored in a counter memory in link with the switch operation, and the amounts of opening and closing of the side support can be adjusted quickly and easily by switch operations.