To repair a flooring material adjacent to a sill of a sash of a sweeping-out window, while leaving an existing aluminum sash.

In this floor structure 1, a sash-side fitting recess 3, which is formed at one edge of a waterproof flooring material 2, is fitted into an indoor-side edge 6, elongated to the indoor side, of the sill 5 of the sash 4 in which the sweeping-out window is mounted; and an indoor-side fitting protrusion 7, which is formed at the other edge of the waterproof flooring material 2, is fitted into one groove 9 of the flooring material 8 which is laid in a room. A drainage slope 10, which is directed to one edge from the other edge, is formed on the top surface of the flooring material 8, and a protrusive streak 11 is provided near the other edge, so as to block dew condensation water.