To improve transmission torque and fixation strength between a cylindrical body and a shaft only by press fitting work.

In a press fitting structure for a shaft and a cylindrical body, a first cylindrical body 21 and a second cylindrical body 22 that axially come into contact with each other and continue to each other are press fitted to the shaft 16 so as to enable rotation and fixation. This structure is characterized by installing irregularities 21c, 22c that engage with each other on abutment faces 21d, 22d of the first cylindrical body 21 and the second cylindrical body 22. Preferably, the irregularities are unevennesses 21c, 22c formed on the abutment faces 21d, 22d of the first cylindrical body 21 and the second cylindrical body 22 and engaging with each other. More preferably, the shaft is a counter shaft 16 of a transmission 10, and either one of the first cylindrical body 21 or the second cylindrical body 22 is a counter drive gear 21 of the transmission 10.