To provide a soap which allows secure attachment of a soap piece, which has become thin, small and difficult to use, to a new soap so that the small soap piece can be exhausted as a part of the new soap.

An indentation having a depth of ≥5 mm and an area of from 100 to 1,500 mm2 is formed on a soap. On use, a soap which became thin and small and a new soap are soaked in hot water of ≥40°C. As soon as the surfaces of both soaps become sticky and the softening of the soap fragment can be felt by the fingers, the soap fragment is deformed and pressed onto the indentation of the soap. Since the adhesion force of each soap is increased compared with that achieved by simply sticking them together, they do not separate when rubbed onto hands or towels.