A testing method for testing a semiconductor device includes heating the semiconductor device until the temperature of the semiconductor device reaches a predetermined temperature; conducting other functional tests other than testing of the overheat protection function in a second step after the temperature of the semiconductor device has reached the predetermined temperature; allowing the semiconductor device to generate heat by itself such that the overheat protection function of the semiconductor device is activated, detecting a first diode forward voltage of a desired diode contained in the semiconductor device when the overheat protection function of the semiconductor device is activated and computing a first computational temperature of the semiconductor device based on the detected first diode forward voltage of the desired diode contained in the semiconductor device; and determining whether the computed first computational temperature of the semiconductor device resides in the overheat protection function activating temperature range.