To provide a means for manufacturing a hollow core that is used to manufacture a casting having a cavity portion and has a hollow portion therein to improve its operability, which means can achieve an almost uniform thickness of a shell portion irrespective of the shape of the hollow core, and as a result, can carry out a stably continuous casting work while preventing the generation of tears, pores, deformation, etc. of the hollow core.

The die 50 for manufacturing the hollow core has projecting portions 55, 56 on a cavity forming surface 58. The projecting portions 55, 56 are provided with insert dies made of a material having a thermal conductivity higher than those of die bodies (a movable die 51 and a fixed die 53).