PURPOSE: To discharge effectively corpuscles within arm portions without dispersion or the like and heighten the degree of cleanness, by providing a discharge means whose purpose is to discharge to the outside corpuscles within the arm portions through the hole of a joint.

CONSTITUTION: A fan provided at a base is operated, and air AF taken in from the outside of an arm portion 1(J5) is made to flow into the next arm portion 1(J4) through the passing hole (1) of a joint J5 between the arm portions 1(J4)-1(J5). Next, air current AF is sent in, in order from the arm portion 1(J4) to 1(J3)→1(J2), and finally is made to reach the fan of the base, and discharging to the outside is made by means of the fan. Accordingly, the whole of the inside of robot arm portions is made to be of negative pressure by the operation of the fan, and by means of air current following this, corpuscles generated by the joint portion and a belt or the like within arm portions 1(J2)-1(J5), can be all discharged effectively from within arm portions 1(J2)-1(J5) to an outside duct.