To eliminate the necessity for a care-given person to float the waist for wiping-off after easing nature even in an O type toilet seat by suspending the inner collar edge by the inner peripheral edge, and carving a longitudinal directional recessed groove on a front upper surface in a plan view almost egg shape.

In a plan view almost egg-shaped auxiliary toilet seat 1, an inner layer is composed of a high forming polyurethane foaming body, and a skin layer is composed of a low foaming polyurethane foaming body. The inner peripheral edge 11 having the length of 3 cm is suspended over the whole periphery on the inner peripheral edge of the auxiliary toilet seat 1, and an almost circular arc-shaped cutout part 12 is arranged in a rear part of the inner peripheral edge 11 and on the lower end of both side parts. A longitudinal direction recessed groove 13 having a rear end width of about 10 cm and the depth of 2 cm is carved on a front upper surface of the auxiliary toilet seat 1. When using such an auxiliary toilet seat 1, it works well when the toilet seat is inserted and fitted between the inner collar edge 11 and the outer collar edge 14 by inserting the inner collar edge 11 into a through hole of an O type toilet seat, so that complicated installing work is not required.