To provide a water receiving tray for simplifying execution, eliminating water leakage, reducing the number of components and preventing moisture inside a bathroom from flowing into a bathtub back space.

The water receiving tray comprises: an attaching port (1) provided on the side face of a bathtub (Y); a flange member (3) provided with a flange (3a) which is a detachment stopper to the attaching port (1) to be inserted into the attaching port (1); the water receiving tray (4) provided on the side face with an insertion hole (5) to which the flange member (3) is inserted; watertight packing (6) provided between the peripheral edge of the attaching port (1) of the bathtub (Y) and the peripheral edge of the insertion hole (5) of the water receiving tray (4); and an attaching member (7) for attaching the water receiving tray (4) and the flange member (3) to the bathtub (Y). The bathtub (Y) and the water receiving tray (4) are interposed between the flange (3a) of the flange member (3) and the attaching member (7), and the water receiving tray (4) and the flange member (3) are attached to the bathtub (Y).