PROBLEM TO BE SOLVED: To provide a connection part, a holding arm, and a holder which enable turning of a first arm member and a second arm member for holding a body to be held, and enable restriction of the turning of the first arm member and the second arm member.SOLUTION: A holder 1 having a holding arm 2 where a first arm member 10 and a second arm member 11 are turnably connected to each other at a connection part 14, includes a turning restriction member 19 which is brought into contact with the first arm member 10 and the second arm member 11 in a pressurized state to restrict turning of the first arm member 10 and the second arm member 11, and enables the turning of the first arm member 10 and the second arm member 11 when the pressurized state is released.
