To provide a rotary solenoid for reducing the rotational energy of a rotor with a simple structure so as to enhance the reliability and decrease the cost.

The rotary solenoid 10 is provided with a rotary shaft 18, a permanent magnet 20 fixed integrally with the rotary shaft 18, a spring 21 for energizing the rotary shaft 18 in one of circumferential directions, a yoke 12 formed with a pair of stator parts 14A, 14B opposed to the permanent magnet 20 at a prescribed gap width and on which a coil 30 is wound, and power application control means 36, 37 for controlling application of power to excite or not to excite selectively the coil 30. In the solenoid 10, the permanent magnet 20 is magnetized in its radial direction.