To provide a bathtub for easily washing only the buttocks in a seated state using warm water when an old person who wears a diaper, soils the diaper, simplifying post-treatment of soil water or the like, and easily carried.

This buttocks washing bathtub for care is constituted by installing a small bathtub part 1 formed with seat parts 3 in right and left positions of a bottom part and provided with a plug implement 7 mounted to a warm water discharge hole, fittingly on a legless chair part 11 having a back plate part 8, elbow placing parts 9 and an elliptic through hole 12 at the center part, engaged in a chair form, and enclosing a recessed box shaped legless chair container part 13 that can collect and store soil warm water or the like, under the legless chair part 11.