Provided is a power supply box device that improves design properties by keeping an operation lever from being visible from outside and that prevents misoperations caused by the operation lever being touched by mistake. A power supply box device 1 that comprises a plug 30: that has an operation lever 31m that protrudes in a radiation direction from a plug main body and extends downward; and that is supported by a lid member so as to be capable of forward and reverse rotation. A box main body has: a housing 12 that houses a power supply; and a lever cover 13 that is supported by the housing 12 so as to be capable of ascending/descending between a lock position that is on an upper side and a lock release position P2 that is on a lower side. The lever cover 13 is arranged in the lock release position P2 to allow the operation lever 31 m to rotate and covers the operation lever 31m by ascending, relative to the operation lever as arranged in a prescribed position, from the lock release position to the lock position.