The present invention relates to a method of adjusting backlash and a gear mechanism constructed by the backlash adjusting method. An idler gear (18) is against a first gear (73) and a second gear (17) with a flexible film (60) being held therebetween so that the idler gear is led to a meshing engagement position. When the film (60) is removed, a gear gap according to the thickness of the film (60) can be constructed, between the first gear and second gears (73 and 17) and the idler gear (18). A gear mechanism comprises a mover/stopper (20) capable of moving the idler gear (18) in a radial direction perpendicular to axial directions and toward the meshing engagement position.