To provide an arm operating mechanism allowing an arm to suitably conduct a specified operating by a simple structure, regardless the length of the arm.

This arm operating mechanism comprises a first arm 1A supported by a supporting potion 47 at a base end portion 10a, and capable of rotating about a center axis C1 of the supporting portion 47; a link base 5 connected to a tip end portion 11a of the first arm 1A through a first connecting portion 7A; a second arm 2A having a base end portion 20a connected to the link base 5 through a second connecting portion 7B; a parallel link 4A keeping the link base 5 at a prescribed attitude, and a motor M for driving. The motor M is mounted on the link base 5, and the link base 5 is provided with a mechanism portion 6 generating rotation force about a center axis C2 of the first and second connecting portions 7A, 7B on the first and second arms 1A, 2A by driving force of the motor M.