To resolve problems of garbage treatment apparatuses wherein, in most of conventional vertically rotating agitation and mixing systems of a horizontal shaft type, securing of a capacity sufficient to treating volume needs a depth and a width matching the capacity, causing difficulty in introducing an apparatus matching the treating volume in a place with a small installation area.

This garbage treatment apparatus uses a double agitation tank comprising inner and outer tanks as an agitation tank of the garbage treatment apparatus. A screw type agitation vane by a vertical shaft is used for an agitating mixing shaft of the inner tank to horizontally agitate, and performs vertical agitation and mixing from the inner tank to the outer tank, and from the outer tank to the inner tank.