Rotating arm mechanism and robot

The invention provides a rotating arm mechanism and a robot. The rotating arm mechanism comprises a rotating arm body; the rotating arm body is of a columnar structure; the rotating arm body is provided with an accommodating cavity; the accommodating cavity extends to the two ends of the rotating arm body; and the rotating arm body is of a hollowed structure. For the rotating arm mechanism, by configuring the rotating arm body to be of the hollowed structure, the hollowed rotating arm body structure enables a space of the accommodating cavity to be relatively large and also reduces self weightof the rotating arm body, so that reduction on the overall body size and the overall weight of the rotating arm mechanism is facilitated, the structural compactness of the rotating arm mechanism is strengthened, and lightweight of the rotating arm mechanism is realized; and as the rotating arm mechanism is applied to the robot, the problems of relatively large overall size and heavier weight of the robot in the prior art