<p>Provided are a process and an apparatus capable of easily concentrating sludge to high concentrations. The sludge-concentrating method includes: a residue separation step that separates the sludge into residue and sludge from which has residue has been removed; a chemical blending/flocculating step that blends chemicals into the sludge from which residue has been removed; and a concentrate separation step that separates solids and liquids in the concentrated sludge produced by the chemical blending/flocculating step into thickened sludge and separated liquid. The sludge-concentrating apparatus includes a residue separation unit that separates the sludge into residue and sludge from which residue has been removed, a chemical blending/flocculating unit that blends chemicals into the residue-removed sludge, and a concentrate separation unit that separates solids and liquids in the concentrated sludge produced by the chemical blending/flocculating unit into concentrated sludge and separated liquid.</p>
