A resin encapsulating apparatus for semiconductor devices is characterized by including a rectangular pot constituted by being surrounded with two opposed wall surfaces of short side each having an outwardly projecting curved surface and two opposed wall surfaces of long side which are each substantially in the form of a straight line; a plurality of cavity lines connected respectively through gates to the bottom portion of at least one said long-side wall surface of the pot, the cavity lines each consisting of cavities connected in series; and a plunger to be inserted into the pot.