To simplify determination of drive parameters upon driving a motor for which circuit constants are unknown, and shorten the time required in determination. A parameter determination support device includes: an automatic measurement means for automatically measuring a D-phase current (A), DC link voltage (V) and Q-phase voltage command (%) of the motor drive device, as operating information upon driving the synchronous motor at a substantially constant speed under each condition of a first condition based on a base speed, and a second condition in which the D-phase current (A) of the motor drive device was changed from the first condition, according to the test-run program, by applying the initial parameter; an estimation means for estimating a short circuit current (Arms) and a D-phase inductance (mH), as circuit constants of the synchronous motor, based on the operating information; and a calculation means for performing calculation of an optimum parameter tailored to the output specification of the synchronous motor, based on the circuit constants.