A second enclosure can be folded over a first enclosure based on the rotation around a rotation axis defined relative to the first enclosure. A protrusion member is guided on the second enclosure along a straight line between first and second positions. A receiving hole is defined in the first enclosure so as to receive the insertion of the protrusion member protruding out of the front or back surface of the second enclosure. Even if one end of the protrusion member collides against the first enclosure during the fold of the second enclosure over the first enclosure, the protrusion member is caused to move. The first enclosure is thus prevented from suffering from damages or scratches over the first enclosure.