A connection mechanism is provided with a plate member formed with a polygonal hole, the plate member including a first plate and a second plate overlaid with each other, each of the first plate and the second plate being formed with the polygonal hole, a shaft member formed with a polygonal column section fitted in the polygonal hole formed on the plate member, and a fixing mechanism that fixes the first plate and the second plate with each other to retain a status where the first plate and the second plate are urged oppositely in a rotational direction about a central axis of the shaft member.
