The present invention is to provide a toner for developing an electrostatic image, having good fixing property and shelf stability, as well as having a good transferring property without decreasing its printing concentration nor generating a fog, even where it is subjected to a printing condition exposed under various circumstances and for an extended period. The toner of the present invention comprises a colored particle including a rosin ester having an acid value of 2 or less; and an external additive. The rosin ester used in the present invention is an electrification compound of a rosin compound with a polyalcohol. The electrification compound of the rosin ester may be reacted with an epoxy compound. The colored particle has a core-shell structure. The colored particle further comprises a binder resin, a colorant, a charge control agent, a parting agent in the core, and a magnetic material in the core.