A power semiconductor device that uses a lead frame for making connection to a semiconductor device and has a structure less subject to fatigue failure at the connection part of the lead frame. A mold resin of a casing (14) is used for integrally covering the lead frame (6, 7, 13), semiconductor device (1), and metal block (15) serving as a substrate mounting the semiconductor device (1). The mold resin surrounding the lead frame (6) and semiconductor device (1) strengthens the joint therebetween, resulting in the power semiconductor device less subject to fatigue failure at the connection part of the lead frame (6).