Of carrier liquids extracted by an carrier liquid extracting device from a liquid developer obtained by mixing together yellow, cyan, magenta, and black liquid developers, the carrier liquid of particularly high purity is recycled for concentration control of the yellow liquid developer and the carrier liquid of purity a little lower than the aforementioned purity is recycled for concentration control of the cyan, magenta, and black liquid developers. A carrier liquid extracted from the yellow liquid developer is recycled for the concentration control of the yellow liquid developer, and a carrier liquid extracted from the liquid developer obtained by mixing together the cyan, magenta, and black liquid developers is recycled for the concentration control of the cyan, magenta, and black liquid developers. This permits efficient use of carrier liquids to be recycled without having an influence on the image quality.