Electric actuator and rotation control mechanism

An electric actuator, comprising:

• a motor, having a motor shaft that extends in an axial direction;
• a speed reduction mechanism that is linked to a portion of the motor shaft on one side in the axial direction;
• an output part to which rotation of the motor shaft is transmitted via the speed reduction mechanism;
• and
• a rotation detection device that detects rotation of the output part,
• wherein the output part extends in the axial direction and is disposed on the one side in the axial direction with respect to the motor shaft;
• the rotation detection device comprises:
• a magnet that is fixed to the output part and extends in a circumferential direction of the output part, and
• a rotation sensor that faces the magnet in the axial direction or a radial direction;
• the magnet has a plurality of magnetic poles disposed in the circumferential direction, and
• at least one magnetic pole of the magnet is disposed at a predetermined angular position with respect to an angle reference position of the output part in a rotation direction.