PURPOSE: To realize magnitudes of shocks and frequencies simulating real operation with a comparatively small-capacity hydraulic cylinder by connection with a proper play a cab supporting truck and a piston rod.

CONSTITUTION: Forward translation motions are provided to a wheeled truck 1 in an intermittent manner, by switching a solenoid change-over operating valve 25 with a timer 29, and switching a 3-position change-over valve 19 to a range between forward F and neutral N positions or between forward F and retarding R by advancing and retarding of piston rod 23 of air cylinder 21. At a joint of wheeled truck 1 and piston rod 11 shocks are generated onto the truck 1 when the piston rod 11 operates intermittently leaving a play 1b and thus shocks are given to a cab 7 on the truck simulating roughly real operation with a comparatively small-capacity hydraulic cylinder 9. Varied setting times of timer 29, amounts of strokes of hydraulic cylinder 9 and magnitudes of play 1b cause changes to oscillation mode and magnitude of shocks given to the cab 7.