A method of manufacturing a rotary electric machine armature that includes a cylindrical armature core in which a plurality of slots that extend in an axial direction are disposed in a circumferential direction and a coil wound around the armature core, the slots having respective radially opening portions that open in a radial direction, and the coil being constituted by joining a plurality of segment conductors to each other, the method comprising: a preparation step of preparing a plurality of the segment conductors and preparing the armature core, the segment conductors having respective conductor side portions that extend along the axial direction and respective crossover portions connected to the conductor side portions on an outer side of the armature core in the axial direction, the conductor side portions being provided with respective joint portions that have respective facing surfaces; a regulation member arrangement step of arranging a regulation member that has a regulation surface disposed in accordance with a position, in the radial direction, of the conductor side portion positioned most on a side of the radially opening portion, the regulation surface regulating movement of the conductor side portions in the radial direction; an insertion step of inserting, when the segment conductor, among the plurality of segment conductors, the crossover portion of which is disposed on one side in the axial direction with respect to the armature core, is defined as a first segment conductor and the segment conductor, the crossover portion of which is disposed on the other side in the axial direction with respect to the armature core, is defined as a second segment conductor, at least either the conductor side portions of the first segment conductor or the conductor side portions of the second segment conductor into the slots such that the facing surface of one of the joint portions of the first segment conductor and the facing surface of one of the joint portions of the second segment conductor face each other; a joint step of joining the joint portions of the first segment conductor and the joint portions of the second segment conductor to each other, and a regulation surface moving step of moving the regulation surface toward an opposite side from a side of the radially opening portion in the radial direction, the regulation surface moving step being performed after the insertion step and before the joint step, wherein the insertion step includes the regulation surface of the regulation member regulating movement of the conductor side portions in the radial direction until the facing surface of one of the joint portions of the first segment conductor and the facing surface of one of the joint portions of the second segment conductor face each other, and characterized in that the insertion step is performed after the regulation member arrangement step. a preparation step of preparing a plurality of the segment conductors and preparing the armature core, the segment conductors having respective conductor side portions that extend along the axial direction and respective crossover portions connected to the conductor side portions on an outer side of the armature core in the axial direction, the conductor side portions being provided with respective joint portions that have respective facing surfaces; a regulation member arrangement step of arranging a regulation member that has a regulation surface disposed in accordance with a position, in the radial direction, of the conductor side portion positioned most on a side of the radially opening portion, the regulation surface regulating movement of the conductor side portions in the radial direction; an insertion step of inserting, when the segment conductor, among the plurality of segment conductors, the crossover portion of which is disposed on one side in the axial direction with respect to the armature core, is defined as a first segment conductor and the segment conductor, the crossover portion of which is disposed on the other side in the axial direction with respect to the armature core, is defined as a second segment conductor, at least either the conductor side portions of the first segment conductor or the conductor side portions of the second segment conductor into the slots such that the facing surface of one of the joint portions of the first segment conductor and the facing surface of one of the joint portions of the second segment conductor face each other; a joint step of joining the joint portions of the first segment conductor and the joint portions of the second segment conductor to each other, and a regulation surface moving step of moving the regulation surface toward an opposite side from a side of the radially opening portion in the radial direction, the regulation surface moving step being performed after the insertion step and before the joint step, wherein the insertion step includes the regulation surface of the regulation member regulating movement of the conductor side portions in the radial direction until the facing surface of one of the joint portions of the first segment conductor and the facing surface of one of the joint portions of the second segment conductor face each other, and characterized in that the insertion step is performed after the regulation member arrangement step.