To provide a unit and a system for drying/volume-reducing organic waste, by each of which the organic waste can be dried easily and the volume of the organic waste can be reduced by simple constitution.

This unit 30 has a vessel main body 31 in which the organic waste W is thrown, an electric heater 34 (a heating means) for heating the waste W thrown in the body 31, an agitating means 35 for agitating the waste W thrown in the body 31 in the horizontal and vertical directions and a plurality of ceramic balls B (crushing elements) for crushing the waste W and reducing the volume of the waste W while being agitated together with the waste W. This system 1 is provided with the unit 30 and organic waste drying units 10, 20 which are installed at the preceding stage of the unit 30 for drying the waste W so that the units 10, 20, 30 communicate with one another.