Provided is a wafer test method for a power switch that can measure the current flowing in a main IGBT and a detection current flowing in an IGBT for current detection simply in the same manner as a state of actual operation. In this wafer test method for a power switch, an IGBT (2) for current detection that detects the current value for a main IGBT (1) is integrally formed on the same semiconductor substrate. A resistance means that makes the emitter current of the IGBT (2) for current detection flow in the emitter terminal (6) of the main IGBT (1) is provided. Electricity is made to flow simultaneously in the main IGBT (1) and the IGBT (2) for current detection, and a constant current is applied to the common collector terminal for the main IGBT (1) and the IGBT (2) for current detection. The current ratio (main current/detection current) for the main current of the main IGBT (1) and the IGBT (2) for current detection is calculated from the current flowing in the IGBT (2) for current detection, which is found from the voltage across the resistance means and the constant current.