A roll rotation structure for rotationally driving, in a roll direction of a robot, an arm unit mounted on a shoulder part of the robot through a roll support part comprises a linear motion actuator having an output shaft that moves linearly, a mounting part by which the linear motion actuator is mounted on the shoulder part in such a manner that a main body of the linear motion actuator is located at the side of a main body of the robot adjacent to the shoulder part, and that the output shaft of the linear motion actuator can be drawn into and out of the shoulder part, and a connection part that connects the output shaft and the arm unit in such a manner that an output from the output shaft of the linear motion actuator produces an angular moment in the roll direction in the roll support part.