A resolver comprising: a metallic stator core having a ring shape, a plurality of magnetic pole teeth provided on an internal circumferential face of the stator core, winding wires including lead wires; and a resin mold on which the winding wires are wound around the plurality of the magnetic pole teeth, the resin mold including: tooth portions that respectively cover the magnetic pole teeth, a ring portion that connects the tooth portions each other, the ring portion covering at least one end face of the stator core; a connector projecting outward in a radial direction from the ring portion, the connector including metal terminals, and the lead wires being connected to the metal terminals, the lead wires being fixed to the ring portion and the connector, and the resolver being characterized in that the resin mold further comprises a stress reduction structure arranged at a connecting portion between the ring portion and the connector in which at least a part of the resin in the stress reduction structure is fitted to the metallic stator core, the stress reduction structure being configured to reduce tensile stress applied to the lead wires due to thermal expansion in the radial direction of the ring portion, wherein the stress reduction structure is provided with a constriction, and in the constriction, the width of the connecting portion as viewed in an axial direction of the stator core is constricted such that the quantity of resin at the connecting portion is reduced and an elongation of the resin mold in the radial direction is suppressed by the metallic stator core. a metallic stator core having a ring shape, a plurality of magnetic pole teeth provided on an internal circumferential face of the stator core, winding wires including lead wires; and a resin mold on which the winding wires are wound around the plurality of the magnetic pole teeth, the resin mold including: tooth portions that respectively cover the magnetic pole teeth, a ring portion that connects the tooth portions each other, the ring portion covering at least one end face of the stator core; a connector projecting outward in a radial direction from the ring portion, the connector including metal terminals, and the lead wires being connected to the metal terminals, the lead wires being fixed to the ring portion and the connector, and the resolver being characterized in that the resin mold further comprises a stress reduction structure arranged at a connecting portion between the ring portion and the connector in which at least a part of the resin in the stress reduction structure is fitted to the metallic stator core, the stress reduction structure being configured to reduce tensile stress applied to the lead wires due to thermal expansion in the radial direction of the ring portion, wherein the stress reduction structure is provided with a constriction, and in the constriction, the width of the connecting portion as viewed in an axial direction of the stator core is constricted such that the quantity of resin at the connecting portion is reduced and an elongation of the resin mold in the radial direction is suppressed by the metallic stator core. tooth portions that respectively cover the magnetic pole teeth, a ring portion that connects the tooth portions each other, the ring portion covering at least one end face of the stator core; a connector projecting outward in a radial direction from the ring portion, the connector including metal terminals, and the lead wires being connected to the metal terminals, the lead wires being fixed to the ring portion and the connector, and the resolver being characterized in that the resin mold further comprises a stress reduction structure arranged at a connecting portion between the ring portion and the connector in which at least a part of the resin in the stress reduction structure is fitted to the metallic stator core, the stress reduction structure being configured to reduce tensile stress applied to the lead wires due to thermal expansion in the radial direction of the ring portion, wherein the stress reduction structure is provided with a constriction, and in the constriction, the width of the connecting portion as viewed in an axial direction of the stator core is constricted such that the quantity of resin at the connecting portion is reduced and an elongation of the resin mold in the radial direction is suppressed by the metallic stator core.