To provide an excretion aid which is more suitable for indoor use.

In this excretion aid, a treatment tub 31 is equipped under the seat part 3 of the chair 1 to enable excretion to drop into a base material 69 stored with microorganisms in the treatment tub 31. The stored matters in the treatment tub 31 including the excretion are stirred with a stirrer 34 and decomposed by the microorganisms. The stirrer 34 has at least a first stirring blade 39 to push out the stored matters in a side near the center of rotation toward the circumference side of the treatment tub 31 by rotation and a second stirring blade 40 push up the stored matters in the circumference side of the treatment tub 31 along the circumference side part of the treatment tub 31 by rotation so as to efficiently stir the stored matters in the treatment tub 31.