To embed and eliminate a personal computer main body from a desk top plate (an operation surface, a connection surface remain) and to flatten the desk top plate and an upper surface of the personal computer main body.

An optical disk drive (1), a power switch (2), a power supply unit (3), an I/O connector group (4) of a mother board and an expansion slot (6) are provided on the upper surface of a personal computer case. An opening in which the personal computer (8) is put is made on the desk top plate (11) and the personal computer is inserted into the opening.