Abstract: A rotation transmitter using balls comprises a worm gear having a ball circulation path, a large number of metal balls inserted into the ball circulation path in a continuous row, a worm wheel having a large number of ball recesses for accommodating balls on the periphery thereof and meshed with the worm gear via the metal balls, collars provided at the opposite ends of the worm gear, and ball guides of semicircular sectional configuration provided to project tangentially from the collars and cover the ball ports of the worm gear. The ball circulation path is constituted of a helical ball race formed on the outer surface of the worm gear, ball ports formed at the ends of the ball race and a ball circulation passage provided to extend diagonally through the interior of the worm gear at a position offset toward the surface of the worm gear from the axis thereof so as to cause the openings at the opposite ends of the ball circulation passage to connect with the ball ports at an obtuse angle.