Abstract: Provided is an arm structure of an industrial robot in which the same wrist element is enabled to have a plurality of types of characteristics, thus allowing a variation model to be readily implemented. An arm structure of an industrial robot with a plurality of wrist elements, the arm structure being provided with, in a housing: a first motor and a second motor that drive the plurality of wrist elements respectively; a first gear that is attached to a first output shaft of the first motor and has an external diameter equal to that of the first output shaft; and a second gear that is attached to a second output shaft of the second motor and has an external diameter equal to that of the second output shaft. The second motor is disposed in front of the first motor and is disposed such that the axis of the second output shaft is laterally offset with respect to the axis of the first output shaft. A space portion is provided to the rear of each of the first motor and the second motor.