A liquid developer includes toner particles formed of a resin material and a coloring agent, and an insulation liquid in which the toner particles are dispersed, the insulation liquid containing ester-exchange oil obtained by an ester-exchange reaction of soybean oil and at least one of semidrying oil and nondrying oil. It is preferred that the insulation liquid further contains fatty acid monoester. Further, it is preferred that the amount of the fatty acid monoester contained in the insulation liquid is in the range of 5 to 50 wt %.