To simply put a display, etc. in and out in a computer which is constituted to be used as a normal flat desk and to use a computer on it at need.

An opening 7 of a proper size is opened at the top plate 2 of a flat desk, a lid plate 8 is pivotally attached to the opening so as to freely stand, open and close backward and a vertically moving unit 20 capable of mounting a display 26 in this opening so as to vertically move by a motor 16 is provided. Then, a frame 27 which contacts with the lower surface of the lid at the time of elevating of the vertically moving unit for standing the lid plate in an opening state is stood on this vertically moving unit.