PURPOSE: To improve fixing property and a coating film forming property by incorporating 1-20 wt.% aliphatic polyester oligomer with the amount of thermoplastic resin.

CONSTITUTION: The aliphatic polyester oligomer is mixed into a toner particulate forming resin at a ratio of 1-20 wt.% of the thermoplastic resin. Preferable aliphatic polyester oligomers are the polymers with the molecular weight of 1,000-10,000 and the saturated aliphatic polyester oligomers consisting of saturated aliphatic diols and saturated aliphatic dicarboxylic acids and preferably without incorporating a crosslinking group in the structure. Thus the self-fixing property and film forming property are simultaneously improved.