A squirrel-cage induction motor, comprising: a rotor core comprising two types of rotor cores (1, 51), the rotor cores (1, 51) comprising slots (2, 52) extending in an axial direction of the rotor core (1, 51) in an outer circumferential side of the rotor core (1, 51), wherein one type of rotor core is disposed at both axial-direction sides of the other type of rotor core and sandwiches the other type of rotor core, wherein the slots formed by the one type of motor core have a different cross sectional shape from the slots formed by the other type of the rotor core so that at least one axially extending unevenness is formed at least at a radially outer portion of each of both radially extending side walls of the slots (2,52); and a rotor conductor having a rod shape and inserted in each slot (2,52) of the slots (2, 52), wherein after insertion of the rotor conductor in the slot (2,52), a flared portion is formed in an outer circumferential side of the rotor conductor by flaring of the conductor in a transverse direction of the slot (2,52), and the rotor conductor is fixed to the slot (2,52) by a force of propping occurring between the flared portion (4, 54) of the rotor conductor (4, 54) and the both side walls of the slot (2,52), for each of the slots (2, 52), the flared portion (4, 54) is abutting at least one unevenness disposed along the axial direction of the rotor core (1, 51), the unevenness comprising at least one recess, wherein the flared portion (4, 54) is formed centrally in the axial direction in the outer circumferential side of the rotor conductor, wherein the flared portion (4, 54) includes a portion abutting the recess and a further portion which is the flared portion except for the portion abutting the recess, and wherein the portion abutting the recess is flaring wider in a transverse direction of the slot (2, 52) than the further portion, wherein the length of the further portion with respect to the axial direction is longer than the length of the portion abutting the recess with respect to the axial direction, and wherein the flared portion abutting the recess is formed at the portion of the core slots formed bv the other type of the rotor core and the further flared portion is formed at the portion of the core slots formed by the one type of rotor core. a rotor core comprising two types of rotor cores (1, 51), the rotor cores (1, 51) comprising slots (2, 52) extending in an axial direction of the rotor core (1, 51) in an outer circumferential side of the rotor core (1, 51), wherein one type of rotor core is disposed at both axial-direction sides of the other type of rotor core and sandwiches the other type of rotor core, wherein the slots formed by the one type of motor core have a different cross sectional shape from the slots formed by the other type of the rotor core so that at least one axially extending unevenness is formed at least at a radially outer portion of each of both radially extending side walls of the slots (2,52); and a rotor conductor having a rod shape and inserted in each slot (2,52) of the slots (2, 52), wherein after insertion of the rotor conductor in the slot (2,52), a flared portion is formed in an outer circumferential side of the rotor conductor by flaring of the conductor in a transverse direction of the slot (2,52), and the rotor conductor is fixed to the slot (2,52) by a force of propping occurring between the flared portion (4, 54) of the rotor conductor (4, 54) and the both side walls of the slot (2,52), for each of the slots (2, 52), the flared portion (4, 54) is abutting at least one unevenness disposed along the axial direction of the rotor core (1, 51), the unevenness comprising at least one recess, wherein the flared portion (4, 54) is formed centrally in the axial direction in the outer circumferential side of the rotor conductor, wherein the flared portion (4, 54) includes a portion abutting the recess and a further portion which is the flared portion except for the portion abutting the recess, and wherein the portion abutting the recess is flaring wider in a transverse direction of the slot (2, 52) than the further portion, wherein the length of the further portion with respect to the axial direction is longer than the length of the portion abutting the recess with respect to the axial direction, and wherein the flared portion abutting the recess is formed at the portion of the core slots formed bv the other type of the rotor core and the further flared portion is formed at the portion of the core slots formed by the one type of rotor core.