PURPOSE: To enable a pan to be positively manufactured with ease without creating any interstice between the tile and the disc body.

CONSTITUTION: A water prevention pan 1 is provided with tiles 4 spread over the disc body 5, wherein a mold 2 with projections 21 is prepared on the periphery of a floor surface forming part 20, and a lattice-like spacer 3 is put on the floor surface forming part 20, and then the titles are fitted in each interstice of the spacer 3 so that the surface of the tiles is directed to the floor surface forming part 20 and surround the spacer 3 and tiles 4 with projections 21. After that, a fiber reinforced plastics material is laminated on these surfaces to then be cured for forming a disc body 5, and joints 7 are formed by placing cement material into grooves 6 formed by the spacer 3 and projections 21 after releasing the disc body 5 from the mold 2.