PURPOSE: To perform quick and efficient cap closing motion of many sealed containers by forcedly rotating the clamp head provided at the free end of an arm capable of free swing by driving source.

CONSTITUTION: The body member 11 of a pot placed on a table 36 is held by a clamp jaw 42 and fixed. Then, a swing arm 48 holding cap member 13 having been cleaned is swang to the position of the holding member 11 and lowered. After that, the cap member 13 is forced to contact with the opening edge of the body 11 of the pot by the shrinkage force of a cylinder 45. At the same time, a cylinder 64 is shrinked to rotate a clamp head (clamp hand) 49 provided at the end of the swing arm 48 along with the cap member 13 to mesh the hook member of the cap member 13 with the plate of the body 11 projected to be meshed obtaining a close packing condition (sealing condition).