To solve the problem that normal pressing suction cups comprising a bowled part and an outside attachment part integrally molded of soft resin have uniform hardness, and materials selected for better conformance to contact surfaces have a weak force of return, to thereby result the need for an increased holding force.

A fin 1 is formed in the shape of a suction cup bored in the center, and a cylinder 2 slightly larger than the bore is inserted into the bore. This applies an outward pressing force to the center of the bored suction cup to increase a thickness and increase hardness in succession from the portion of the largest force. The force of return increases accordingly to thereby increase the holding force of the suction cup.