PURPOSE: To provide cost reduction by reducing the number of part items.

CONSTITUTION: An electromagnetic proportional valve 20 and a pressure regulator 30 are arranged in parallel to the direction of acceleration/deceleration (a) based on engine load, and pressure regulating level is changed according to inertial force working upon spools 23, 32 and a plunger 22 to generate hydraulic pressure Pc according to the acceleration/deceleration (a) or the engine load. It is thus possible to make it unnecessary to use a means for detecting the engine load and a means for introducing the detected results into hydraulic pressure.