A rotor structure, comprising: a rotation shaft body in which a blade groove is formed at an outer circumference part of the rotation shaft body rotatable around an axis line, and which extends in a circumferential direction of the axis line, wherein a width dimension of a groove opening side of the blade groove is set to be smaller than a width dimension of a groove bottom side of the blade groove; and a plurality of blade bodies (20,20A,20B) which are arrayed in the circumferential direction at the outer circumference part of the rotation shaft body and have blade roots fitted into the blade groove respectively; wherein a blade fixing piece is installed so as to be positioned between at least one set of adjacent two blade bodies (20,20A,20B) in the circumferential direction inside the blade groove, one of an opening wall part of the groove opening side of the blade groove and the blade fixing piece is provided with a projected part, and the other of them is provided with a recessed part which is fitted with the projected part, the blade fixing piece includes a displacement mechanism which is configured to allow the projected part to removably fit to the recessed part, the displacement mechanism includes an advance-retract axle which is capable of being screwed towards the groove bottom of the blade groove, and an end face of the advance-retract axle that faces the groove bottom of the blade groove swells out to the groove bottom of the blade groove, and the opening wall part of the blade groove is provided with a concaved portion as the recessed part, said concaved portion extending in the radial direction of the axis line at least on one side in the width direction of the blade groove, characterized in that the blade fixing piece is provided with a screw member as the projected part, said screw member projecting in the radial direction of the axis line at least on one side in the width direction of the blade groove. a rotation shaft body in which a blade groove is formed at an outer circumference part of the rotation shaft body rotatable around an axis line, and which extends in a circumferential direction of the axis line, wherein a width dimension of a groove opening side of the blade groove is set to be smaller than a width dimension of a groove bottom side of the blade groove; and a plurality of blade bodies (20,20A,20B) which are arrayed in the circumferential direction at the outer circumference part of the rotation shaft body and have blade roots fitted into the blade groove respectively; wherein a blade fixing piece is installed so as to be positioned between at least one set of adjacent two blade bodies (20,20A,20B) in the circumferential direction inside the blade groove, one of an opening wall part of the groove opening side of the blade groove and the blade fixing piece is provided with a projected part, and the other of them is provided with a recessed part which is fitted with the projected part, the blade fixing piece includes a displacement mechanism which is configured to allow the projected part to removably fit to the recessed part, the displacement mechanism includes an advance-retract axle which is capable of being screwed towards the groove bottom of the blade groove, and an end face of the advance-retract axle that faces the groove bottom of the blade groove swells out to the groove bottom of the blade groove, and the opening wall part of the blade groove is provided with a concaved portion as the recessed part, said concaved portion extending in the radial direction of the axis line at least on one side in the width direction of the blade groove, characterized in that the blade fixing piece is provided with a screw member as the projected part, said screw member projecting in the radial direction of the axis line at least on one side in the width direction of the blade groove.