PURPOSE: To achieve a quick measurement of output characteristic with limited error by selecting voltage and current ranges in the measuring system by performing a specified preliminary measurement to choose the optimum measuring range accurately for a short time.

CONSTITUTION: When with voltage and current ranges set at max., voltage the same as that on the side of the cathode of an auxiliary power source 6 for forced short-circuiting is applied to a gate with a gate voltage control mechanism 4 to turn OFF an FET, the output terminal of a solar battery to be measured connected between terminals 7 and 9 is opened. Consequently, a fine current for forced opening in the opposite direction of the output current flows to the solar battery through a constant current source 5. At this point, when the voltage across output terminals of the solar battery is read with a voltage detector 10, the max. range voltage based on the open voltage is given irrelevant to internal resistance of the solar battery. Likewise, the max. range current is selected based on the short-circuit current. Thus, a quick measurement of the output characteristic of the battery can be performed with limited errors depending on the selection of the optimum range determined accurately for a short time by this preliminary measurement.