A shaft coupling mechanism for coupling first and second rotating shafts (2, 4) by being disposed between the first and second rotating shafts (2, 4) so as to transmit a rotation of the first rotating shaft to the second rotating shaft, comprising: a first coupling base body which is coupleable to the first rotating shaft, a second coupling base body which is coupleable to the second rotating shaft, and an intermediate interposed member which is interposed between said first and said second coupling base bodies (3, 5), wherein said first coupling base body has a first base portion and a first axial projecting portion formed integrally with the first base portion in such a manner as to project in an axial direction from one axial surface of the first base portion toward the second coupling base body, said second coupling base body has a second base portion and a second axial projecting portion formed integrally with the second base portion in such a manner as to project in the axial direction from one axial surface of the second base portion toward the first coupling base body, the first axial projecting portion and the second axial projecting portion are disposed with an interval therebetween in a direction about an axis, and said intermediate interposed member has a third base portion interposed between the first base portion and the second base portion in the axial direction, at least a pair of radial projecting portions formed integrally on the third base portion in such a manner as to be spaced apart from each other in the direction about the axis and project radially from an outer peripheral edge of the third base portion, a third axial projecting portion formed integrally on the third base portion in such a manner as to project in the axial direction from one axial surface of the third base portion, and a forth axial projecting portion formed integrally on the third base portion in such a manner as to project in the axial direction from another axial surface of the third base portion, each of the pair of radial projecting portions of said intermediate interposed member having a smaller rigidity than the rigidity of the first and second axial projecting portions (13, 18) and being elastically deformable, at least one of the first rotating shaft and the first base portion of said first coupling base body at its one axial surface being in contact with an axial surface of the third axial projecting portion, while at least one of the second rotating shaft and the second base portion of said second coupling base body at its one axial surface being in contact with an axial surface of the forth axial projecting portion, and wherein the first axial projecting portion of said first coupling base body is disposed in one circumferential gap between adjacent radial projecting portions in the direction about the axis, is in contact with both one side surface in the direction about the axis of one radial projecting portion and another side surface in the direction about the axis of another radial projecting portion at its both side surfaces (21, 22) in the direction about the axis, extends across and beyond the other axial surface of the third base portion, and, at its axial distal end surface, opposes the one axial surface of the second base portion of said second coupling base body with a clearance therebetween, while the second axial projecting portion of said second coupling base body is disposed in another circumferential gap between adjacent radial projecting portions in the direction about the axis, is in contact with both another side surface in the direction about the axis of the one radial projecting portion and one side surface in the direction about the axis of the other radial projecting portion at its both side surfaces (23, 24) in the direction about the axis, extends across and beyond the one axial surface of the third base portion, and, at its axial distal end surface, opposes the one axial surface of the first base portion of said first coupling base body with a clearance therebetween, characterized in that said intermediate interposed member has one protrusion formed integrally on and projecting in the axial direction from the one axial surface of the third base portion and another protrusion formed integrally on and projecting in the axial direction from the other axial surface of the third base portion, the one protrusion forming a clearance, which is smaller than the corresponding clearance, between its axial distal end surface and the one axial surface of the first base portion of said first coupling base body, while the other protrusion forming a clearance, which is smaller than the corresponding clearance, between its axial distal end surface and the one axial surface of the second base portion of said second coupling base body.