Provided is a motor rotor which, without changing an integral fastening structure relying on swage pins, increases resistance to the excessive excitation force of the motor rotor and which can easily prevent decreases in fastening strength; a motor that uses the motor rotor, and an electric compressor are also provided. This motor rotor is provided with a cylindrical rotor core comprising multiple laminated magnetic steel sheets, end plates and balance weights laminated on both ends of the rotor core, and multiple headed swage pins which are inserted from one side and which integrally fasten the rotor core, the end plates and the balance weights. The material of the balance weight arranged to the head of the swage pin is harder than that of the swage pin, and the material of the balance weight arranged to the swage part of the swage pin is softer than that of the swage pin.