A shock absorber (A1, A2, A3, A5) for a propeller unit driven by a propeller shaft of a vessel propulsion apparatus, the shock absorber (A1, A2, A3, A5) comprising: a damper made of an elastic material, the damper being disposed between an outer peripheral surface of a bushing (40, 140, 540) of the propeller unit and an inner peripheral surface of an inner hub (20, 120) of the propeller unit, the damper including: a first portion facing the bushing (40, 140, 540) in a circumferential direction of the bushing (40, 140, 540); a second portion facing the inner hub (20, 120) in the circumferential direction; and a deformation-absorbing space (S1, S2) that is deformable in a state in which the damper has been elastically deformed by relative rotation between the bushing (40, 140, 540) and the inner hub (20, 120), characterized in that the first portion is facing a rib (43,143) of the bushing (40, 140, 540) in a circumferential direction of the bushing (40, 140, 540); the second portion is facing a rib (22, 122) of the inner hub (20, 120) in the circumferential direction; and the damper includes a connection portion (b) by which the first portion and the second portion are connected to each other; wherein the deformation-absorbing space (S1, S2) is defined between the first portion and the second portion in a state in which the damper has not been elastically deformed by relative rotation between the bushing (40, 140, 540) and the inner hub (20, 120); and the deformation-absorbing space (S1, S2) is deformable such that the first portion and the second portion approach each other in the state in which the damper has been elastically deformed by relative rotation between the bushing (40, 140, 540) and the inner hub (20, 120), wherein a pair of dampers are disposed on the outer peripheral surface of the bushing (40, 140, 540) and are spaced apart in the circumferential direction; and a first connection arm is provided by which first end portions of the pair of dampers are connected to each other in an axial direction of the bushing (40, 140, 540). a first portion facing the bushing (40, 140, 540) in a circumferential direction of the bushing (40, 140, 540); a second portion facing the inner hub (20, 120) in the circumferential direction; and a deformation-absorbing space (S1, S2) that is deformable in a state in which the damper has been elastically deformed by relative rotation between the bushing (40, 140, 540) and the inner hub (20, 120), characterized in that the first portion is facing a rib (43,143) of the bushing (40, 140, 540) in a circumferential direction of the bushing (40, 140, 540); the second portion is facing a rib (22, 122) of the inner hub (20, 120) in the circumferential direction; and the damper includes a connection portion (b) by which the first portion and the second portion are connected to each other; wherein the deformation-absorbing space (S1, S2) is defined between the first portion and the second portion in a state in which the damper has not been elastically deformed by relative rotation between the bushing (40, 140, 540) and the inner hub (20, 120); and the deformation-absorbing space (S1, S2) is deformable such that the first portion and the second portion approach each other in the state in which the damper has been elastically deformed by relative rotation between the bushing (40, 140, 540) and the inner hub (20, 120), wherein a pair of dampers are disposed on the outer peripheral surface of the bushing (40, 140, 540) and are spaced apart in the circumferential direction; and a first connection arm is provided by which first end portions of the pair of dampers are connected to each other in an axial direction of the bushing (40, 140, 540).