The present invention relates to the wrist device of a robot which has speed reducers (52-56, 62-66) built in a wrist portion (7) and which attains three degrees of rotating freedom orthogonal to one another, and is characterized in that three transmission shafts (41, 51a, 61a) penetrating through the interior of an arm (3) are arranged in parallel with one another as power transmission means within the arm (3).
