A rotor for a dynamo-electric machine, the rotor comprising: a shaft; and a rotor core constituted by laminating a plurality of electromagnetic steel sheets, the rotor core being configured such that the shaft is attached to the inner periphery of the rotor core, wherein: each of the electromagnetic steel sheets constituting the rotor core includes an insertion hole into which the shaft is inserted, and a key protruding radially inwardly from the insertion hole; the shaft includes a keyway formed along an axial direction and having opposite side faces; the shaft is attached by clearance fit to the insertion holes of the electromagnetic steel sheets; the key includes an extension portion protruding radially inwardly from the insertion hole, and projection portions extended outwardly in a width direction of the extension portion from opposite side faces of the extension portion in the width direction, and the key is fitted by pressing into the keyway such that each of the side faces of the key abuts with a corresponding one of the side faces of the keyway, characterized in that the key further includes a protruding portion protruding radially inwardly from a distal end of the extension portion. a shaft; and a rotor core constituted by laminating a plurality of electromagnetic steel sheets, the rotor core being configured such that the shaft is attached to the inner periphery of the rotor core, wherein: each of the electromagnetic steel sheets constituting the rotor core includes an insertion hole into which the shaft is inserted, and a key protruding radially inwardly from the insertion hole; the shaft includes a keyway formed along an axial direction and having opposite side faces; the shaft is attached by clearance fit to the insertion holes of the electromagnetic steel sheets; the key includes an extension portion protruding radially inwardly from the insertion hole, and projection portions extended outwardly in a width direction of the extension portion from opposite side faces of the extension portion in the width direction, and the key is fitted by pressing into the keyway such that each of the side faces of the key abuts with a corresponding one of the side faces of the keyway, characterized in that the key further includes a protruding portion protruding radially inwardly from a distal end of the extension portion. each of the electromagnetic steel sheets constituting the rotor core includes an insertion hole into which the shaft is inserted, and a key protruding radially inwardly from the insertion hole; the shaft includes a keyway formed along an axial direction and having opposite side faces; the shaft is attached by clearance fit to the insertion holes of the electromagnetic steel sheets; the key includes an extension portion protruding radially inwardly from the insertion hole, and projection portions extended outwardly in a width direction of the extension portion from opposite side faces of the extension portion in the width direction, and the key is fitted by pressing into the keyway such that each of the side faces of the key abuts with a corresponding one of the side faces of the keyway, characterized in that the key further includes a protruding portion protruding radially inwardly from a distal end of the extension portion.