To provide a connecting structure between an existing waterproof pan and a strut when the existing waterproof pan at least remains unchanged for being recycled to newly redecorate an old bath-room unit.

In the connecting structure between the existing waterproof pan and the bath-room unit strut when the old bath-room unit is redecorated, a longer reinforcing member 1 bent at an approximately right angle is mounted on the wall attaching surface 6a of the existing waterproof pan 6, a vertical section 1b of the reinforcing member 1 is fixed to the rising wall 6b of the waterproof pan with a clamping tool 5, the bath-room unit strut (corner strut 7 and flat strut 8) is fixed to the rising wall 6a of the waterproof pan with the clamping tool 5 via a fixed section (7a/8a) of the lower part thereof.