PURPOSE: To provide reinforced resin having very smooth surface by using molds in which the upper surface has smaller porting characteristic than the inner surface, as a pair of the half mods of resin injection molding.

CONSTITUTION: One of a pair of half molds (preferably obverse surface half) in which the obverse side has smaller parting characteristic is supported in upward pasture and reinforcing materials such as glass fiber continuous strand mat, surface mat and glass cloth are placed thereon and then reverse surface mold is placed with its mold surface directed downward. At this time, if necessary the mold is clamped by a clamp to form a predetermined cavity between both molds using a spacer or gasket and reinforcing material is held in the mold. Then, liquid resin is injected into the mold and is heated as required to be hardened.