Provided is an electric power conversion device which has a cooling unit in which a plurality of electronic devices that generate heat are disposed, and which enables a required installation area to be reduced and enables cooling flow path routing to be simplified. The electric power conversion device (1) of the present invention is provided with: a cooling unit (2) being an internally hollow rectangular column having a refrigerant inlet portion (2c) and a refrigerant outlet portion (2e) and internally having a refrigerant flow path (2f) through which a refrigerant flows from the refrigerant inlet portion (2c) toward the refrigerant outlet portion (2e); electronic devices (3) disposed respectively on three or more outer side surfaces of the cooling unit (2) except for a refrigerant inlet surface (2b) on which the refrigerant inlet portion (2c) is disposed and a refrigerant outlet surface (2d) on which the refrigerant outlet portion (2e) is disposed, the electronic devices (3) being cooled by boiling of the refrigerant; and a hollow outer case (4) covering the electronic devices (3).