To provide an artificial aggregate where the elution of chromium is satisfactorily reduced even when a waste raw material containing chromium is used, and its manufacturing method.

When a waste comprising chromium-containing incineration ash or treated soil is used as a raw material, the waste is mixed with a granular reducing agent in such a manner that the resultant raw material mixture has a content of the reducing agent of 5-30 mass%, granulated and baked, to form an artificial aggregate having an elution amount of hexavalent chromium of 0.05 mg/L or less. Coal incineration ash, coke ash, heavy oil ash, garbage incineration ash, sewage sludge incineration ash, paper sludge incineration ash, waste plastics incineration ash or treated soil can be used as the chromium-containing incineration ash or the like. One or more of coal, coke, activated carbon, wood charcoal, plastics and refuse derived fuel (RDF) can be used as the reducing agent.