An electric power converter for a vehicle, including a semiconductor element from which a motor drive current is output, a drive circuit that drives the semiconductor element, a control circuit that controls the drive circuit, a capacitor that smooths a DC current to be input to the semiconductor element, a container housing the semiconductor element, the drive circuit, the control circuit and the capacitor, a refrigerant retained in a state of vapor-liquid two-phase equilibrium within the container, and a heat exchanger unit that condenses the refrigerant in a vapor phase to be a liquid phase and exchanges heat with outside, wherein the semiconductor element, the drive circuit, the control circuit and the capacitor are disposed in a positional arrangement that will leave the semiconductor element, the drive circuit, the control circuit and the capacitor immersed in the refrigerant as the electric power converter is installed in the vehicle, and the heat exchanger unit is disposed at a side of a wall of the container forming a vapor-phase space.