An electric power conversion apparatus includes first and second electric power conversion devices and a housing. The first and second electric power conversion devices are arranged to overlap each other in an overlap direction. The housing receives both the first and second electric power conversion devices therein. The housing has a partition wall that extends between the first and second electric power conversion devices to partition the housing into first and second parts in which the first and second electric power conversion devices are respectively received. The partition wall has a coolant passage formed therein, thereby allowing a coolant to flow through the coolant passage.