A power transistor driving apparatus includes: a field-effect type transistor; an insulated gate type bipolar transistor, which is connected to the field-effect type transistor in parallel; a first driving circuit generating a first gate voltage to turn on the insulated gate type bipolar transistor, the first gate voltage applied to a gate of the insulated gate type bipolar transistor; a second driving circuit adjusting a second gate voltage to turn on or off the field-effect type transistor, the second gate voltage applied to a gate of the field-effect type transistor; a detection circuit detecting whether the insulated gate type bipolar transistor is turned on when the first driving circuit generates the first gate voltage. The second driving circuit generates the second gate voltage to turn on the field-effect type transistor when the detection circuit detects that the insulated gate type bipolar transistor is turned on.