To provide a coupler of an encoder capable of preventing vibration or impact.

In the coupler of an encoder, an encoder shaft 6 constituting a rotating part of the encoder, composed of a fixed part and a rotating part, is connected to a rotating shaft 2 of a motor. The encoder shaft 6 and the rotating shaft 2 of the motor are arranged to face each other through a gap in axial direction. The axial end face of the encoder shaft 6 and the axial end face of the rotating shaft 2 of the motor, facing each other, are provided with magnets 11 and 12, respectively.