PURPOSE: To form an image high in quality and to enhance fixability of an image by using a binder consisting essentially of a resin obtained by polymerizing specified two kinds of monomers in the presence of apolymn. initiator in an aliphatic hydrocarbon solvent.

CONSTITUTION: The binder used for the developer is prepared by polymerizing at least a monomer A represented by formula 1 having ≥2 points having reaction activities different from each other, with another monomer B represented by formula 2 having solvatability in aliphatic hydrocarbon solvents, preferably, in an A/B ratio by weight basis of (1W30)/(99W70), in the presence of a polymn. initiator in the heated aliphatic hydrocarbon solvent. As a result, since the monomer B forms a polymer solvatable in the aliphatic solvents, a copolymer having a cross-linked structure comes to be dispersed in the aliphatic hydrocarbon solvents.