PURPOSE: To make it possible to check performance without taking off a pump from the system by controlling working speeds of an actuator etc. so as to be able to obtain delivery flow rate necessary to check performance of a hydrau lic pump with a computer, and judging the delivery pressure at that time.

CONSTITUTION: A computer detects revolution speed to seek for flow rate flowing in a motor for the hydraulic motor 4, and for an actuator 3, detects stroke quantity for detecting operation speed from such as variation per hour to get flow rate through multiplying the speed into a pressure receiving area of a piston. And then, the same controls the system so that the sum of these flow rates may become in regulated delivery flow rate Q. Still more, the computer 2 judges whether delivery pressure P of a hydraulic pump when sum on flow rates flowing in a hydraulic system coincides with regulated delivery flow rate Q of the hydraulic pump, is in a range of regulated value P1, P2 or not, and outputs information to be deteriorated in performance of the hydraulic pump 1 when the pressure is out of the range, and built-in test can be easily performed.