To provide a board case configured to prevent opening thereof even if an external force in the opening direction is applied to a case sealing portion without breakage of a pin member.

A case body 20A for holding a control board has a front opening sealed by a cover 20B. The cover 20B is fixed to the case body 20A by a locking mechanism provided at an edge of the opening side opposite to a pivot side so that the cover is not opened. The locking mechanism has built-in locking pin units 40 held at the edge of the opening side of the case body 20A in a direction crossing the opening/closing direction of a cover 20B. The built-in locking pin unit 40 has a locking pin 41 urged toward the front end. When the cover 20B is closed, the locking pin 41 is retracted by a tapered portion 28B of a pawl portion 26B provided as a pin-operating portion 22B at the edge of the opening side, and the locking pin 41 projects and fits to a fitting portion 27B provided on the back side of the tapered portion 28B.