Abstract: The agitator of the present invention comprises: a drive source; a differential unit; a rotation-direction switching unit; and a brake unit. The drive source generates rotational driving forces. The differential unit and rotation-direction switching unit are positioned in a driving-force transmission path between agitation vessels containing agitation-target material. The brake unit alternately stops the rotation of two rotating shafts extended from the differential unit. Here, the differential unit of the agitator has functions of receiving the rotational driving forces from the drive source and transmitting the rotational driving forces to the two rotating shafts in a differential manner. The rotation-direction switching unit has a function of inverting the rotation direction of the rotational driving forces transmitted to the agitation vessel while the rotation of the rotating shaft is being stopped by a brake.