Disclosed is a battery device including a battery enclosure incorporating a battery cell. The battery device further includes an output terminal that outputs power of the battery cell. The battery enclosure includes a first surface, a second surface, a first step surface, a second step surface, a first engaging portion, a second engaging portion, a first groove, and a second groove formed in the second step surface and the second engaging portion, and a recess is provided in at least one of the first step surface and the second step surface.