An electric machine capable of easily and efficiently assembling a rotor core to a rotating shaft is provided. A rotor core is formed by laminating a first steel plate consisting of one or more electromagnetic steel plates having a first protrusion portion to be accommodated in a groove portion of a rotating shaft and a second steel plate consisting of one or more electromagnetic steel plates having a second protrusion portion to be accommodated in the groove portion of the rotating shaft. The first protrusion portion of the first steel plate has a first engaging portion deformed by a side surface of the groove portion of the rotating shaft. At least a part of the first engaging portion of the first steel plate is disposed in a space formed between a second protrusion portion of the second steel plate and the side surface of a groove portion of the rotating shaft.