A kneading apparatus has a pair of rotary shafts mounted to undergo rotation in different directions of rotation and at different rotational speeds from one another. Stirring members are helically arranged on outer peripheries of the rotary shafts at predetermined helical and angular pitches for kneading an object during rotation of the rotary shafts. The helical pitch of the stirring members of one of the rotary shafts has an inverse helix from that of the stirring members of the other rotary shaft. The stirring members have surfaces with a first phase configured to move the kneaded object in a feed direction or a second phase symmetrical to the first phase and configured to move the kneaded object in a direction reverse to the feed direction. The stirring members are arranged so that the first and second phases cyclically repeat in a predetermined sequence in axial directions of the rotary shafts.