A horizontal articulated robot has a plurality of horizontal arms coupled by joint shafts, and a working shaft disposed at the extreme end of an extreme end arm among the horizontal arms has mounting portions of an end effector formed to both the upper and lower ends thereof. With this arrangement, there can be provided a horizontal articulated robot that can cope with various work transport forms and various types of works by one type of a robot by selectively using the upper and lower sides of a working shaft.