To secure the carrying force of almost spherical non-magnetic one- component developer while preventing the almost spherical non-magnetic one- component developer from being deteriorated in an image forming device constituted so that an image is formed by using the almost spherical non-magnetic one-component developer.

This laser printer is constituted so that toner T being as the non-magnetic one-component developer is triboelectrified and carried to the surface of a photoreceptor drum 23 by rotating a supply roller 28 and a developing roller 27 while bringing them into contact with each other. The roller 28 is the sparse foaming roller having open cells whose number is less 30 pieces per inch. Since large pressure force does not act on the toner T, the toner T is prevented from being deteriorated. Besides, since the toner T is the suspension polymerization toner being extremely near to a sphere and 0.5 weight % or more of hydrophobic silica whose average grains size is ≤30 nm is added, the toner T is extremely excellent in flowability. Thus, even when the toner T enters the cells of the roller 28, it can immediately get out and it can be excellently carried.