A developing machine is provided which includes a supporting case (2); a developing sleeve (4) mounted within the supporting case (2), for carrying a developing agent (3); a magnetic roller (15) mounted within the developing sleeve (4); a projection (5d) for thinning a layer of the developing agent (3) carried on the developing sleeve (4) and regulating the amount of the developing agent (3); a drift portion A having a predetermined capacity, in which the developing agent (3) stopped by the projection (5d) drifts about; a toner containing portion (5b) having a toner supplying opening 5c which faces the developing sleeve (4) and is contiguous to the drift portion A on the upstream side of a direction in which the developing agent (3) on the developing sleeve (4) is carried; a developing agent storage case (5) attachable to and detachable from the supporting case (2), including the developing sleeve (4) and the toner containing portion (5b); and a developing agent retrieving device for a scraping the developing agent (3) lying on the developing sleeve (14) and retrieving the scraped developing agent (3) into the toner containing portion (5b).