The disclosure relates to an accessory which can be attached and detached from the camera body. The camera body includes a body-side terminal group, body-side fittings, and multiple body-side protrusions. The accessory includes accessory-side fittings, cylindrical parts, accessory-side terminal sets, and the first to fourth accessory-side protrusions. The accessory is attached to the camera body by rotating a first angle in a first direction from the insertion position to the attachment position in a plane substantially orthogonal to the optical axis at a predetermined position on the opticalaxis. Viewed from the optical axis direction, the second center angle is smaller than the first angle. The second center angle is defined by the straight line connecting one end of the second accessory side protrusion with the optical axis and the circumferential direction of the second accessory side protrusion The other end is formed by a straight line connecting the optical axis. The accessory-side terminal group is arranged inside a partial area of the cylindrical part, and only one end of the first accessory-side protrusion is located outside the partial area. The circumferential ends ofthe first to fourth fitting-side protrusions are arranged in 4 areas divided by the first straight line on the fitting side and the second straight line on the fitting side.