To support two gears on a shaft with a short axial direction supporting span in such a way as involving no eccentricity or inclination.

A gear supporting structure according to the invention is to support a first gear 42 and second gear 41 on the shaft 40 in alignment and with its turning hindered, wherein engagement with the shaft is established by a first fitting part 42c and a turn stopping part 42b where the first gear furnished with a boss part 42a extending in the axial direction is formed in other position and the alignment fitting is performed. The second fitting part 41c of the second gear is put in alignment fitting on the boss part and meshing with the first gear is made by an engaging means 43 in face-to-face mating. This allows decreasing the supporting span of the second gear, and the alignment accuracy and perpendicularity of the two gears with respect to the shaft are enhanced.