PURPOSE: To carry out a further high initial strain correction and balancing of a joint shaft by carrying out strain correction in relation to a center line further precisely approximated to the center line produced at the time when the joint shaft is installed in a vehicle.

CONSTITUTION: A joint shaft 10 is supported in a freely rotatable way by an end part on the opposite side to a center pipe shaft 16 and a center shaft supporting bearing assembly 24 which supports the center tube shaft of the joint shaft in a freely rotatable way. The joint shaft is rotated relative to an indicator 28 as to measure the mismatching in the radius direction. The mismatching in the radius direction is measured at one or plurality of points along the center pipe shaft. Force is applied to the joint shaft and the joint shaft is permanently sagged, so that the observed mismatching in the radius direction can be lessened.