To provide a desk which neither narrows down its leg space nor spoils its outward appearance as a desk even when a personal computer main body is fitted below the tabletop where a drawer should be arranged.

A personal computer main body 2 has personal constituent components put in a case 3 apparently in a drawer shape and is equipped with a switch board which is inserted perpendicularly into the insertion slot 46a of a fixed connector 46; when an extension board 5A is postfitted to a mother board 41, the extension board is arranged on the mother board nearly horizontally and electrically connected through the switch board 6 in a state similarly to a case wherein it is inserted directly into the insertion slot 46a of the fixed connector 46 in the perpendicular direction.