To provide an installation structure of a hand wash basin reducing the cost by dispensing with installation of a back board such as a back guard in the hand wash basin, providing an installation state with superior design and facilitating attachment/detachment in maintenance.

This hand wash basin 1 installed with its back face 1a abutting on a wall 2 is disposed with a water stop 11 between the back face 1a of the hand wash basin 1 and the wall 2, the water stop 11 is watertightly fixed to the wall 2 by a cutoff tape in the back face of the water stop 11, and the back face 1a of the hand wash basin 1 is so installed as to detachably abut on a packing 12 provided in the front face of the water stop 11.