A printer (1), which uses a toner containing a compound that undergoes a phase transition after cis-trans isomerization caused by absorbing light, is provided with a light-sensitive drum (2) that conveys the toner, a UV LED (11) that radiates UV light having a wavelength of at least 300nm and less than 400nm, and a heating roller (12) that presses paper (P) holding the toner image exposed by the UV LED (11). Thus enabled is the conservation of energy during image formation.
