To produce a cake of soap of the original size by collecting cakes of solid soap turned small after use, and using remnant bath water as an energy source.

A spring shaft 13 is inserted into a transparent plastic cylinder 11 from the top to the bottom thereof, and then fixed by rotating a middle screwed handle 16. Subsequently, a bottom handle is fitted into a bottom portion of the transparent plastic cylinder 11, and then fixed by likewise rotating the same to obtain a soap reprocessing apparatus 10. Additionally stated, in production of soap, when an upper inner lid 52 and a bottom inner lid 51 are inserted and used in such a way that they are outside soap, a cake of soap 53 can be withdrawn without attachment thereof to the soap reprocessing apparatus.