To solve the problem that in the case of a conventional study desk with bookshelf combined with a desk and an independent shelf, the width of a top board is restricted by the width of the bookshelf and sufficient work space on the top board cannot be secured.

An exterior width W1 of a lower bookshelf 18 is narrower than the width W2 inside right and left leg panels 5 and 6 of a desk 2 and the height of the lower bookshelf 18 is lower than that of a lower surface of the top board 4 of the desk 2 from the floor surface. When the system furniture 1 is used as the study desk with a bookshelf, the lower bookshelf 18 is stored in a storage space to be a space below the top board 4 of the desk 2 and between the right and left leg plates 5 and 6 of the desk 2. On the other hand, an upper bookshelf 17 is mounted on the top board 4 of the desk 2. In the system furniture 1, since the width of the top board 4 of the desk 2 is not restricted by the width of the bookshelf 3, the width of the top board 4 can be freely set.