A mold for manufacturing a skin covered foamed plastic seat capable of effectively dealing with the variations in shape and position of the trim ends. The mold includes stopper means for fastening the trim ends attached to the edges of the skin cover, located between the upper mold and lower mold separately from a space into which a liquid foam resin is to be poured, each of the stopper means having a slit through which one trim end is inserted, and a top face portion to which both ends of the trim end are to be hooked.