To provide a mold for manufacturing a magnet rotor, capable of preventing the damage of the rotor caused by injection molding pressure and capable of also dispensing with post-processing after molding.

In the mold for manufacturing the magnet rotor, for integrally molding a shaft port on a cylindrical magnet 1 by inserting the magnet 1 in the cavity 2a of an injection mold to fill the inner diameter part of the magnet 1 with a resin, the cavity 2a is formed from two or more split pieces 2 movable in the outer diameter direction of the magnet.