Disclosed herein is a coraless AC induction motor. The motor comprises a cup type coreless rotor. A rotating shaft is combined wilh the cup type coreless rotor. An induction rod is inserted into the cup type coreless rotor to guide a magnetic flux from the stator effectively. A stator is positioned around the ccreless rotor. The cup type coreless rotor comprises a squirrel cage-shaped conduction cylinder and composite material or polymer resin. The squirrel cage-shaped conduction cylinder is made of material having high electric conductivity, such as aluminum or copper, and has plurality of slots along the axis of the squirrel cage-shaped conduction cylinder. The composite material or polymer resin fills the slots of the squirrel cage-shaped conduction cylinder to make up for the low stiffness of the squirrel cage-shaped conduction cylinder.