An alignment mechanism comprises a rotary unit 61 with a first rotary axis 61c, three power transmission mechanisms 62, and three alignment action units 63. Each power transmission mechanism 62 comprises a first arm 621 and a second arm 622. The first arm 621 includes a first end 621a pivotably supported at a corresponding one of three different positions P11 to P13, and a second end 621b on the opposite side of the first end 621a. The second arm 622 includes a second rotary axis 622c and is pivotably supported on the second end 621b of the first arm 621 at a position different from the second rotary axis 622c. The alignment action units 63 are connected to corresponding second arms. The second rotary axes 622c are at three positions P21 to P23 separated from the rotary unit 61 toward three different directions centered on the first rotary axis 61c.