An apparatus for manufacturing a stator includes a placement table, a supporting member and a resistance heating device. The placement table is configured to have a stator core, which has coil segments and insulators inserted in slots thereof, placed thereon. The stator core is formed of steel sheets that are laminated in an axial direction of the stator core. The coil segments together form a stator coil. The insulators are formed of a material that is foamable upon being heated. The supporting member is configured to support, in the axial direction of the stator core, distal end portions of teeth of the stator core so as to prevent gaps from being formed between the steel sheets forming the stator core. The resistance heating device is configured to heat, through energization of the stator coil, the insulators along with the stator coil and thereby cause the insulators to foam.