apparatus for resin sealing semiconductor devices is disclosed , wherein semiconductor devices such as semiconductor chips are placed in cavities provided in a pair of chase blocks , which are clamped by a press machine through support members capable of elastic compressive deformation . plastic is then injected into the cavities of the chase blocks such as to resin seal the semiconductor devices . also disclosed is a device for resin sealing semiconductor devices , which device comprises : a pair of chase blocks equipped with cavities for holding semiconductor devices , a press machine for pressing the chase blocks against each other through a pair of press surfaces , a plurality of support members adapted to hold the chase blocks over the respective press surfaces of the press machine and to undergo elastic compressive deformation during the press operation of the press machine , and a plastic injector for injecting plastic into the cavities provided in the chase blocks .