A method for mounting a stator core on a generator, the generator having key bars and spring bars disposed between the key bars and a cylindrical frame body, wherein the spring bars are mounted on an inner peripheral surface of the frame body in a longitudinal direction of the frame body with given intervals in a circumferential direction of the frame body, the method comprising: pre-laminating stator core sheets to form a stator core bundle in a given unit; and conveying the stator core bundle laminated in the given unit to mount the stator core bundle on the inner peripheral surface of the frame body, wherein the method further comprises: mounting the key bars on the spring bars pre-built on the frame body, wherein the key bars are mounted on the inner peripheral surface of the frame body by means of the spring bars, and wherein each key bar is disposed between a pair of spring bars; and adjusting a relative distance between the key bars and the spring bars to adjust the alignment of the key bars, wherein the adjusting the relative distance comprises mounting at least one or more first fixing jigs traversely with respect to the key bars on the space between one side of the lower portion of each key bar and one side of the lower portion of one spring bar of the pair of spring bars on which an adjacent key bar is disposed, so as to adjust the alignment of the lower sides of the key bars. pre-laminating stator core sheets to form a stator core bundle in a given unit; and conveying the stator core bundle laminated in the given unit to mount the stator core bundle on the inner peripheral surface of the frame body, wherein the method further comprises: mounting the key bars on the spring bars pre-built on the frame body, wherein the key bars are mounted on the inner peripheral surface of the frame body by means of the spring bars, and wherein each key bar is disposed between a pair of spring bars; and adjusting a relative distance between the key bars and the spring bars to adjust the alignment of the key bars, wherein the adjusting the relative distance comprises mounting at least one or more first fixing jigs traversely with respect to the key bars on the space between one side of the lower portion of each key bar and one side of the lower portion of one spring bar of the pair of spring bars on which an adjacent key bar is disposed, so as to adjust the alignment of the lower sides of the key bars. mounting the key bars on the spring bars pre-built on the frame body, wherein the key bars are mounted on the inner peripheral surface of the frame body by means of the spring bars, and wherein each key bar is disposed between a pair of spring bars; and adjusting a relative distance between the key bars and the spring bars to adjust the alignment of the key bars, wherein the adjusting the relative distance comprises mounting at least one or more first fixing jigs traversely with respect to the key bars on the space between one side of the lower portion of each key bar and one side of the lower portion of one spring bar of the pair of spring bars on which an adjacent key bar is disposed, so as to adjust the alignment of the lower sides of the key bars.