To provide a rotary hydraulic device having the most suitable starting efficiency and provided with a spool valve-type improved gerotor motor for increasing the volumetric efficiency of a motor.

When a motor is operated at low speed and in a high torque mode, it is composed of a gerotor motor provided with a spool valve 45 including a seal land 85 for effectively separating the high pressure range 87 from the low pressure range 89. Change-over openings 81, 83 connected to respective passages communicated with a plurality of volume chambers of the motor are provided, and high-pressure fluid is recalculated to a contactive volume chamber at high speed and in an operation mode having low torque. Therefore, cavitation in a low torque mode can be prevented.