To provide an apron attachment structure of a bathtub facilitating cleaning in the lower part of the bathtub, a check and a maintenance, having a superior water cutoff performance and having no problem in its aesthetic appearance.

In the attachment structure of an apron 10 for partitioning the bathtub 3 and a wash place pan 20 installed on a floor pan 22 and being attached in the side of the bathtub 3 for hiding the front face 3b of the bathtub 3, the apron 10 is constituted of an inner lid 1 having a working window hole 1b, being formed as a frame body 1a and attached to the bathtub body 3, the floor pan 22, and a bathroom wall 24; and an outer lid 2 detachably attached to the inner lid 1 covering the inner lid 1.