PURPOSE: To drive and precisely position a damping force control spool valve at a desired position.

CONSTITUTION: A variable damping force type shock absorber includes a cylinder, a piston defining an upper chamber and a lower chamber cooperating with the cylinder, and a damping force generator. The piston includes a bypass passage 158 connecting the upper chamber and lower chamber, the valve port 88 provided in the middle of the bypass passage, a spool valve 86, which is reciprocatably fitted to the valve port 88 along the axis 14 of the valve port 88 to control the communication of the bypass passage, a rotary type actuator 48, and a motion converter 50 which converts the rotary motion of the actuator into reciprocation motion to reciprocate and position the spool valve 86.