A liquid developer includes an insulation liquid containing a fatty acid monoester and toner particles comprised of a resin material. The resin material is characterized in that a weight-average molecular weight Mw of the resin material is in the range of 20,000 to 200,000, and an amount of a component of which molecular weight M is 10,000 or less contained in the resin material is in the range of 5 to 40 wt %. The liquid developer described above is harmless to the environment. Further, the liquid developer also has superior preservability or storage stability and superior fixing characteristics at a low temperature. An image forming apparatus that can suitably use such a liquid developer is also provided.