Accessory and working machine

The present invention improves workability during mounting. In the accessory (40), an adapter fixing part (44B) of an adapter (44) is configured to be elastically deformable in the radial direction, and is fixed to a mounted part (16) by being deformed inward in the radial direction due to an external force. Therefore, the adapter fixing part (44B) is fastened to the inner side in the radial direction by the clamping part (46B) of the sub-handle (46), and the adapter fixing part (44B) deforms to the inner side in the radial direction and is fixed to the mounted part (16). Moreover, in a fixed state in which the adapter fixing part (44B) is fixed to the first mounted part (16A), the adapter fixing part (44B) is entirely deformed radially inward and pressed against the outer peripheral surface of the first mounted part (16A), and the adapter fixing part (44B) and the first mounted part (16A) can be arranged coaxially. Therefore, the adapter (44) can be centered relative to the central axis (AL) of the mounted p