The invention discloses an automatic measurement device applied to circumference of a diamond wire electroplating roller. The automatic measurement device comprises a frame and also comprises a roller, a motor, a meter counting module, a sensor and a guide module which are mounted on the frame, wherein a sensor pointer mounted on the side of the roller is used for sensing the sensor as a zero point of the circumference of the roller for a first time and sensing the sensor as an end point again after the roller rotates for a cycle; a meter counting wheel on the meter counting module is in closecontact with the bottom of a V-shaped groove of the roller all the time; when the roller rotates, the meter counting wheel rotates along the roller from the zero point of the sensor to the end pointof the sensor; the circumference of the measured roller is obtained by multiplying the number of rotation cycles of the meter counting wheel by the circumference of the meter counting wheel. Through the automatic measurement device, the errors caused by manual measurement are avoided; the wire breaking risk of the client side is reduced; the quality of client side products is improved; and the client complaint data is reduced.