To provide a deck, the structure of which is simplified as well as the adjustment work of which is facilitated in order to make adjustment of the vertical height of the deck easy when assembling the deck of a balcony.

Locking protrusive pieces 5c, 5c are provided projecting outward in a common joist material 3 supporting a number of deck materials 2. A common joist adjustment member 9 is assembled to the locking protrusive pieces 5c, 5c. The common joist adjustment member 9 has a U-shaped cross section and both side faces 13b, 13b thereof are provided with a number of adjustment grooves 14, 14 facing inside and vertically arranged. The adjustment grooves 14, 14 are selected and the locking protrusive pieces 5c, 5c of the common joist material 3 are inserted thereinto, height adjustment in a vertical direction is performed, and the common joist adjustment member 9 is fixed to the common joist material 3 by screws 18. Then, fine-adjustment is performed as necessary by interposing an adjustment wedge 11 between the common joist adjustment member 9 and a floor surface 23 of a balcony. Finally, fixing means 25 for fixing the adjustment wedge 11 is applied.