A method for manufacturing a rotating electrical machine stator including a stator core having a slot; and a coil having a leg part including a held-in-slot part held in the slot and a portion extending from the held-in-slot part, wherein the coil is formed by joining a plurality of segment conductors together, the leg parts of the plurality of segment conductors each are provided with a joint part that is joined to another one of the segment conductors with a conductive joint material that joins by heating, and the method comprises: a resin disposition step (S1, S12) of disposing a resin foam being before foaming on at least either one of an inner surface of the slot and an outer surface of the held-in-slot part facing the inner surface of the slot; a held-in-slot part disposition step (S4, S13) of disposing a plurality of the held-in-slot parts in the slot such that a pair of the joint parts to be joined together face each other and the conductive joint material is disposed between the pair of the joint parts facing each other; and a heating step of heating the resin foam and the conductive joint material after the held-in-slot part disposition step (S4, S13), to foam the resin foam and join the pair of the joint parts together with the conductive joint material, wherein the conductive joint material is configured to join the pair of the joint parts together at a joint temperature higher than a foaming temperature at which the resin foam is foamed, and in the heating step, the resin foam and the conductive joint material are heated by increasing a temperature to the joint temperature, using a single heating device. the coil is formed by joining a plurality of segment conductors together, the leg parts of the plurality of segment conductors each are provided with a joint part that is joined to another one of the segment conductors with a conductive joint material that joins by heating, and the method comprises: a resin disposition step (S1, S12) of disposing a resin foam being before foaming on at least either one of an inner surface of the slot and an outer surface of the held-in-slot part facing the inner surface of the slot; a held-in-slot part disposition step (S4, S13) of disposing a plurality of the held-in-slot parts in the slot such that a pair of the joint parts to be joined together face each other and the conductive joint material is disposed between the pair of the joint parts facing each other; and a heating step of heating the resin foam and the conductive joint material after the held-in-slot part disposition step (S4, S13), to foam the resin foam and join the pair of the joint parts together with the conductive joint material, wherein the conductive joint material is configured to join the pair of the joint parts together at a joint temperature higher than a foaming temperature at which the resin foam is foamed, and in the heating step, the resin foam and the conductive joint material are heated by increasing a temperature to the joint temperature, using a single heating device. a resin disposition step (S1, S12) of disposing a resin foam being before foaming on at least either one of an inner surface of the slot and an outer surface of the held-in-slot part facing the inner surface of the slot; a held-in-slot part disposition step (S4, S13) of disposing a plurality of the held-in-slot parts in the slot such that a pair of the joint parts to be joined together face each other and the conductive joint material is disposed between the pair of the joint parts facing each other; and a heating step of heating the resin foam and the conductive joint material after the held-in-slot part disposition step (S4, S13), to foam the resin foam and join the pair of the joint parts together with the conductive joint material, wherein the conductive joint material is configured to join the pair of the joint parts together at a joint temperature higher than a foaming temperature at which the resin foam is foamed, and in the heating step, the resin foam and the conductive joint material are heated by increasing a temperature to the joint temperature, using a single heating device.