A desk which permits a common use of member elements also by various types of top boards and which has frame bodies (2) supporting a top board (3) and comprising a plurality of frame materials (21, 22, 23), wherein rail grooves (21a, 22a, 23a) as mounting parts are set on these frame materials (21, 22, 23) continuously along the longitudinal direction of these frame materials, and some specified longitudinal positions in these rail grooves (21a, 22a, 23a) are selected so that member mounting devices (4, 5, 6, 7) for mounting thereon those members such as optional parts and top board can be held at these positions.