PROBLEM TO BE SOLVED: To provide a gear mechanism of a fishing reel in which the decrease of an engagement state of a gear is suppressed even when the gear bends, and the wear of the gear is suppressed, and thereby the decrease in strength of the gear can be prevented.SOLUTION: A gear mechanism 12 includes a drive gear 15 (example of a first gear), and a pinion gear 20 (example of a second gear) engaged to the drive gear. The drive gear 15 has multiple first gear teeth 15a comprising a first normal rotation side tooth surface 15b for transmitting power at the rotation of a rotating direction for reeling up a fishing line, and a first reverse side tooth surface 15c of the opposite surface of the first normal rotation side tooth surface 15b. The pinion gear 20 has multiple second gear teeth 20a comprising a second normal rotation side tooth surface 20b engaged to the first normal rotation side tooth surface 15b, and a second reverse side tooth surface 20c opposed to the first reverse side tooth surface 15c in the opposite surface of the second normal rotation side tooth surface 20b. At least one of the first reverse side tooth surface 15c and the second reverse side tooth surface 20c opposing to each other has an interference prevention part.SELECTED DRAWING: Figure 4【課題】釣り用リールのギア機構において、ギアが撓んだ場合でも、ギアの噛み合い状態の低下を抑えるとともに、ギアの磨耗を抑えてギアの強度の低下を防止出来るギアの提供。【解決手段】ギア機構１２は、駆動ギア（第１ギアの一例）１５と、駆動ギアに噛み合うピニオンギア（第２ギアの一例）２０と、を備える。駆動ギア１５は、釣り糸を巻き取る回転方向の回転時に動力を伝達する第１正転側歯面１５ｂ、及び第１正転側歯面１５ｂの反対面の第１逆転側歯面１５ｃ、を含む複数の第１ギア歯１５ａを有する。ピニオンギア２０は、第１正転側歯面１５ｂに噛み合う第２正転側歯面２０ｂ、及び第２正転側歯面２０ｂの反対面に第１逆転側歯面１５ｃと対向する第２逆転側歯面２０ｃ、を含む複数の第２ギア歯２０ａを有する。対向する第１逆転側歯面１５ｃ及び第２逆転側歯面２０ｃの少なくとも一方は干渉防止部を有する。【選択図】図４
