Robot arm mechanism and rotation joint mechanism

The objectives of the present invention are a robot arm mechanism and a robot joint mechanism wherein damage to cables is suppressed and nimble rotation movement is achieved. A support column part 2 provided with a rotation joint part J1 is installed in the base 1 of the robot arm mechanism. The support column part 2 has a support column lower part and a support column upper part. A motor unit 212 is housed in a tubular motor housing part 211 fixed on the support column upper part. One end of a cable 230 that includes a power supply line is fixed to a lower clamp 204 of the support column lower part, and the other end is fixed to an upper clamp 205 on the support column upper part. When the support column upper part is positioned in the center of the movement range, the upper clamp is positioned on a radius line passing through the lower clamp as viewed from above, and the cable is wrapped in a spiral shape on the outer side of the motor housing part from the lower clamp to the upper clamp.