PURPOSE: To easily provide integrated moldings through injection by filling resin through the injection in a gap between a first metal mold plate and a second metal mold plate in which the positional phases of disposed core and cavity regions are deviated by one region from the first metal mold plate.

CONSTITUTION: A shell 29 forming a first hemisphere 25 is constituted of resin filled in a spherical gap 20 or 21 in a metal mold, and a shell 30 forming a second hemisphere 27 is constituted of resin filled in a spherical gap 21 or 20. Thus, an end of the shell 29 constituting the first hemisphere 25 is connected through a connecting body 32, annular body 34 and connecting body 33 to the end of shell 30 constituting the second hemisphere 27, so that a hollow ball with hole 24 has sufficient rigidity to endure impact.