An object of the present invention is to provide an assembly manufacturing device and an assembly manufacturing method capable of reducing error when the actual position of a long member is detected, and precisely setting a reference point and a coordinates system. The long member assembly apparatus provides a plurality of hand parts for gripping a long member, a touch plate for securing the first end of the long member and restricting the movement of the long member in the longitudinal direction, a laser tracker for detecting the installation position of the touch plate, and a reference determining part for determining reference coordinates or reference point to be used in for adjusting the position of the hand parts, based on the installation position of the touch plate detected by the laser tracker.