PURPOSE: To allow the titled device to have a capability for satisfactorily withstanding a rapid repeated stress, reducing mass of a movable part accompanying reduction of an internal force, eliminating thermal sensitivity and a troublesome rubber seal and radiating heat generated by a rapid operation, a capability for inspecting and repairing a domer device in the shortest time and a capability for performing most of repair without disassembling from a can making device.

CONSTITUTION: This domer device 10 is provided with a housing 12 having an opening part 41, an inner die 40 being arranged around a longitudinal ram axis in the inside of the opening part 41, an outer die 38 being arranged on the circumference of the inner die 40 in the inside of the opening part 41, a second to forth springs 110, 116, 118 being arranged on the circumference spaced- apart radially outward from the longitudinal ram axis and suitably engaging with the inner die 40, and an air spring 82 being arranged toward the outside of the housing 12 far from the outer die 38, providing a resilient force to the outer die 38 along a plurality of paths 64 where a plurality of push rods 120 are arranged, being radially arranged in the outside of the longitudinal ram axis and extending longitudinally passing the second, third and fourth springs.