An image forming apparatus which forms an image onto a recording medium using a liquid developer which contains an insulation liquid and toner particles dispersed in the insulation liquid is provided. The image forming apparatus includes a liquid developer storage section for storing the liquid developer therein; a developing section for developing a toner image using the liquid developer supplied from the liquid developer storage section; an image transfer section for transferring the developed toner image formed by the developing section onto the recording medium to form a transferred image thereon; and a fixing section for fixing the transferred image formed on the recording medium onto the recording medium, wherein at least a part of the insulation liquid in the transferred image is oxidized and polymerized to fix the toner particles in the transferred image onto the recording medium. According to the image forming apparatus, it is possible to fix the toner particles onto the recording medium firmly. A method for forming an image onto a recording medium using the liquid developer is also provided.