A vibration damping mechanism allows increase of an absorption amount of vibration energy, with less possibilities of increase in the manufacture cost of a vibration damping weight and of reduction in the strength of a shaft section. Within a cylindrical hollow portion formed inside the shaft section, there are accommodated a plurality of weight members divided from each other along the circumferential direction about the axis of the hollow portion. An urging member is provided for urging the weight members toward the axis such that dividing faces of adjacent weight members are brought into surface contact with each other.