A traction force control method for a traction apparatus according to the present invention that impresses a desired traction force on an object to be hauled via a traction mechanism is provided. The method includes measuring, in a zero traction state in which an impressed traction force that is impressed on the object to be hauled is zero, the impressed traction force with a traction force sensor and outputting a zero traction value. The method also includes generating an added value in which an adjusting output from a control circuit is added to the zero traction force value; providing the added value to a drive circuit of a drive mechanism that drives the traction mechanism and outputting a drive signal that corresponds to the added value; performing adjustment by increasing or decreasing the adjusting output so that the drive signal becomes a reference value that puts the object to be hauled in the zero traction state, setting the zero traction value as a zero point of the zero traction force sensor, and the adjusting output obtained by the adjustment step as a zero point of the control output of the control circuit, respectively.