A coil insertion device includes coil diameter expanders, the coil diameter expanders being configured to insert a coil assembly in a wound state into slots of a stator core by expanding the coil assembly in diameter from inside of the stator core, each of the coil diameter expanders includes: a coil presser that is arranged inside the coil assembly and presses coil end portions of the coil assembly outward from inside to expand the coil end portions in diameter; and a restrictor that is arranged outside the coil assembly, restricts outward movement of the coil end portions expanded in diameter by the coil presser, and sandwiches the coil end portions of the coil assembly inserted in the slots with the coil presser.

A coil insertion device includes coil diameter expanders, the coil diameter expanders being configured to insert a coil assembly in a wound state into slots of a stator core by expanding the coil assembly in diameter from inside of the stator core, each of the coil diameter expanders includes: a coil presser that is arranged inside the coil assembly and presses coil end portions of the coil assembly outward from inside to expand the coil end portions in diameter; and a restrictor that is arranged outside the coil assembly, restricts outward movement of the coil end portions expanded in diameter by the coil presser, and sandwiches the coil end portions of the coil assembly inserted in the slots with the coil presser.