To provide a counter mounting structure capable of simply mounting a long counter even if the protrusion of accommodation cabinet differs and facilitating the counter to be used easily around a hand wash basin.

A hand wash basin 3 is installed protrusively ahead at an accommodation cabinet 1 embedded in the indoor wall surface 2, and a slope 5 is formed on the forward protruding part 4 of the hand wash basin 3, and a recessed part 8 is formed at the rear edge 7 of a long counter 6. The protruding part 4 is set in the recessed part 8 to allow the slope 5 to abut to the front inner edge 9 of the recessed part 8, while the rear edge 7 of the counter 6 allowed is to abut to the indoor wall surface 2.