There is provided a junction box unit that comprises a body to which a power integration unit is attached and a connector cover that positions a connector of a wiring harness with respect to the body. The connector cover comprises a holding portion holding the connector, a mounting portion attached to the body, and a main body to be accommodated therein. The mounting portion comprises an engagement projection and an engagement arm. The engagement projection protrudes from one end of the main body for locking engagement with a locking portion of the junction box body. The engagement arm includes an arm main body having one end continuing to an outer surface of the other end of the main body and a free end. A protrusion is provided at the central portion of the arm main body for locking engagement with the locking portion. When the protrusion is in locking engagement with the locking portion, the other end of the arm main body is positioned more outwardly of the body than the locking portion.