To provide a resin mold component which has a high dimensional precision and high strength and is light in weight.

The resin mold component such as a gear having an annular part 2 has a hollow part 6 formed in the annular part. The hollow part is formed in the annular part by extruding part of a molten resin from a mold cavity by the pressure of a hollow part forming fluid charged in the molten resin in the cavity. In the annular part, a hollow part forming fluid charging spot 8 and a molten resin extruding spot 9 are formed to be separated in the radial direction of annular part. The hollow part is divided into two parts from the hollow part forming fluid charging spot in the annular part, and each part is extended semi-circularly to the molten resin extruding spot or its vicinity. In this way, the annular part can be made a thin-walled hollow structure approximately over its entire circumference.