A robot arm increases a plurality of arm sections that are turnably connected. The arm sections include a plurality of links and an actuator section that turns the plurality of links. The actuator section includes: a cylindrical cover provided on an outer surface; a motor that turns the plurality of links; a motor frame included in the motor; a reduction gear that decelerates rotation from the motor and outputs a torque; a collar fixed to the reduction gear; and a wire body including at least one of a wire and a pipe. At least a part of the wire body is housed between a surface including a first small body section formed by the motor frame and the collar and a surface including a second small body section of the cylindrical cover.