This paper the suction force and characteristics of suction cups according to their shape. The maximum load that can be held by a suction cup varies depending on its outer diameter. This is because the suction force is the product of the contact area and the pressure. We conducted an experiment to compare the bellows type and sponge type suction cups. In the case of the sponge type suction cup, unlike other suction cups, it was confirmed that the suction force decreased after a certain load after grasping. This is because the sponge type suction cup is deformed after suction and the contact area is reduced. The bellows type had a delay in returning after contraction, but it did not affect the suction force. Based on these results, we recommend using bellows type suction cups instead of sponge type suction cups for robot automation in the logistics industry and using them in processes that grasp irregular objects