To simplify the execution of a work at a site by providing a bath room floor pan with a lap margin.

A bath room floor pan is separated into a floor pan 1 for a bath tub on which a bath tub is arranged and a floor pan 2 for a washing place and structure is formed such that the floor pan 1 for a bath tub and a floor pan 2 for a washing place are connected together. In this case, a connection part 8 between the floor pan 1 for a bath tub and the floor pan 2 for a washing place are provided with respective lap margins 5. One lap margin 5 of the floor pan 1 side for a bath tub and the floor pan 2 for a washing place is slid to regulate a level and the lap margins 5 are connected together.