An electric power converter includes a stacked semiconductor unit formed by stacking semiconductor modules and cooling tubes, and a case. The case has a rear wall portion, a front wall portion, and a pair of side wall portions. The rear wall portion has an opening hole formed in a shape that an outer profile of the cooler fits inside. The stacked semiconductor unit has a closing member joined to a rear-most cooling pipe that is disposed on a rear side to close the opening hole, a refrigerant introducing pipe extended rearward from the closing member, and a refrigerant discharging pipe extended rearward from the closing member. The refrigerant introducing pipe and the refrigerant discharging pipe, and the closing member are connected in close contact with each other, and the closing member and the case are in close contact by a seal section.