A casing includes a base, a flip cover pivotably attached to the base, a first member fixed to the flip cover, and a second member fixed to the base. The flip cover is rotatable around an axis of rotation with respect to the base. The first member forms a tip toward the base along a direction perpendicular to the axis of rotation. The second member extends an elongated arm, the elongated arm being crushed by the tip of the first member in an opening process of the flip cover with respect to the base so as to block the flip cover from opening with a rush.