The end edge part on the bathtub side of the washing place floor pan 1 and the end edge part on the washing place side of the bathtub mounting floor pan 2 respectively are overlapped on both end parts of the drain gutter floor pan 3 by making an overlapping margin variable. 洗い場用床パン1の浴槽側の端縁部分及び浴槽載置用床パン2の洗い場側の端縁部分を排水溝用床パン3の両端部分にそれぞれ重ね代を変化自在にして重ね合わせる。 - 特許庁