Abstract: In a rotary servo valve (1) provided with at least two kinds of pump port (33, 39) for high and low pressures, a spool (11) that is free to rotate and free to reciprocate linearly is installed into a spool guide hole (7) of the valve main body (9), a servo motor (15) that rotates and drives the spool and a linear type actuator (13) that reciprocatedly travels are disposed, and the pump ports are selectively changed over by the reciprocation of the spool, and cylinder ports are selectively changed over by the rotation and at the same time the flow rate is controlled.