A power semiconductor device such as power thyristor including a semiconductor substrate which is clamped by first and second conductive members serving as the electrodes as well as heat sinks, and a plurality of heat pipes whose ends are inserted directly into the conductive members. A plurality of semiconductor substrates and temperature compensating plates are alternatively stacked on another and conductive members are provided on outermost temperature compensating plates to form an assembly. The assembly is hermetically sealed by an insulating package formed by an insulator having a corrugated outer surface such that outer surfaces of the conductive members are exposed out of the package. One or more heat pipes are inserted into the insulating package such that electrically insulating cooling medium filled in the heat pipes can be in direct contact with the semiconductor substrates. The heat pipes may be inserted into the conductive members or heat sinks provided in the assembly.