To provide a slant plate for a portable toilet stool supporting leg allowing an elder person and the like to lean forward and strain at stool in a sitting position on the portable toilet stool when the slant plate is attached to the portable toilet stool supporting leg.

The bottom face of a circular base board 11 is tilted, and along the circumferential edge of one half part on the thinner side, a standing wall 12 is arranged semicircularly. In the upper end of the standing wall 12, a flange 13 is extended inward to be mounted to a supporting leg 3 of the portable toilet removably.