A shaft coupling mechanism for coupling a first rotating shaft and a second rotating shaft by being disposed between the first and the second rotating shafts (2, 4) so as to transmit the rotation of the first rotating shaft to the second rotating shaft, comprising: a first coupling base body which is coupled to the first rotating shaft and a second coupling base body which is coupled to the second rotating shaft, a rotation transmitting member; and an elastic member superposed on said rotation transmitting member in an axial direction, wherein the first coupling base body has a first coupling base portion and a first axial projecting portion projecting integrally in the axial direction from the first coupling base portion, and the second coupling base body has a second coupling base portion and a second axial projecting portion projecting integrally in the axial direction from the second coupling base portion, wherein said rotation transmitting member includes a first base portion having a first inner peripheral surface and a first outer peripheral surface which are cylindrical and at least one pair of first radial projecting portions spaced apart from each other in a direction about an axis and extending radially from the first outer peripheral surface, and wherein said elastic member includes a second base portion superposed on the first base portion in the axial direction and having a second inner peripheral surface and a second outer peripheral surface which are cylindrical and at least one pair of second radial projecting portions respectively superposed on the pair of first radial projecting portions of said rotation transmitting member in the axial direction and extending radially from the second outer peripheral surface, characterized in that at least one of the first coupling base body and the second coupling base body has a shaft which extends in the axial direction from a central portion of one axial end face thereof and is passed through a through hole defined by the first inner peripheral surface of the rotation transmitting member and a thorough hole defined by the second inner peripheral surface of said elastic member, the first axial projecting portion being disposed in one gap among gaps between the pair of first radial projecting portions in the direction about the axis and in one gap among gaps between the pair of second radial projecting portions in the direction about the axis, the second axial projecting portion being disposed in another gap among gaps between the pair of first radial projecting portions in the direction about the axis and in another gap among gaps between the pair of second radial projecting portions in the direction about the axis, the second base portion having a smaller rigidity than a rigidity of the first base portion and being elastically deformable, each of the pair of second radial projecting portions having a smaller rigidity than a rigidity of the pair of first radial projecting portions, being elastically deformable, and having a greater width than a width in the direction about the axis of the pair of first radial projecting portions superposed on the pair of second radial projecting portions in the axial direction, the second inner peripheral surface having a smaller diameter than a diameter of the first inner peripheral surface.