Disclosed is a developing unit 6 including a tank containing a liquid toner, a pick-up roller 10 for drawing the liquid toner from the tank, an application roller 11 whose circumferential surface 11a is supplied with the liquid toner by the pick-up roller 10, and a developing roller 12 whose circumferential surface 12a is applied with the liquid toner by the application roller 11. The pick-up roller 10 and the application roller 11 are arranged in parallel to each other and circumferential surfaces 10a, 11a thereof are in contact with each other. The circumferential surfaces 10a, 11a of the pick-up roller 10 and the application roller 11 are formed with a plurality of grooves 13, 14, respectively, which extend continuously in the axial direction X1.