A board unit includes a case accommodating a circuit board. A power terminal connects a lead-out part of a bus bar with a connection terminal of an electric wire. A cover covers the power terminal and has a lateral wall overlapping a peripheral wall part. The lateral surface of the peripheral wall part and the lateral wall includes an engagement protrusion and an engagement recess to be engaged with the engagement protrusion. The lateral wall of the cover includes a latch piece at a position offset from the engagement protrusion or the engagement recess in a longitudinal direction and a latch portion to be latched with the latch piece which restricts displacement of the lateral wall of the cover in a direction away from the lateral surface of the peripheral wall part of the case.