A method of searching for a sync start in an automated manual transmission, may include a slip preparing step of operating, in a parked position, a sleeve and a clutch restrained so as not to rotate into a slip state, an actuator operating step of moving the sleeve toward a clutch gear from a neutral position, a clutch speed determination step of determining whether or not a speed of rotation of the clutch has decreased by the actuator operating step, a stop determination step of determining whether or not a movement of the sleeve that was driven by the actuator operating step has stopped, and a first position determination step of determining a point where the clutch speed determination step determines that the speed of the rotation of the clutch has decreased and the stop determination step determines that the movement of the sleeve has stopped as the sync start.