To provide a pair of system desks consisting of large and small ones, which is able to carry out various kinds of disposition with only a little restraints.

These system desks consist of a pair of large and small desks 1 and 2 whose top boards 3 and 4 are supported by legs 5 and 6 respectively. At the bottom of the legs 6 of the small desk 2, casters 7 are installed so that the small desk 2 is slidable to be under the large desk, and front or side of it. A plural number of projections are set under the bottom side of the top board 3 of the large desk 1 along the left/right direction. An unit of guide board 9 is set on the top side of the top board 4 at the back of the small desk 2 in a way that the guide board can slide along the projections. This means that the small desk 2 is drawable to the front or side of the large desk 1 and consequently, flexible disposition of objects on the small desk 2 can be realized.