An objective of this invention is that even under the condition that a gear is deflected in a gear mechanism of a fishing reel, reduction of a meshing state of gears can be suppressed and wear of gears can also be suppressed, so as to prevent decrease of gear strength. A gear mechanism 12 comprises a driving gear 15 (an example of a first gear) and a pinion 20 (an example of a second gear) meshing with the driving gear. The driving gear 15 comprises a plurality of first gear teeth 15a. The plurality of first gear teeth 15a include a first forward-rotating side tooth surface 15b which transmits power during rotating in a rotation direction of winding a fishing line and a first backward-rotating side tooth surface 15c on an opposite surface of the first forward-rotating side tooth surface 15b. The pinion gear 20 comprises a plurality of second gear teeth 20a. The second gear teeth 20 includes a second forward-rotating side tooth surface 20b meshing with the first forward-rotating side tooth surface 15b and a second backward-rotating side tooth surface 20c which is at an opposite surface of the second forward-rotating side tooth surface 20b and is opposite to the first backward-rotating side tooth surface 15c. At least one of the first backward-rotating side tooth surface 15c and the second backward-rotating side tooth surface 20c that are opposite to each other is provided with an interference-proof portion.本發明之課題在於，於釣具用捲線器的齒輪機構中，即便於齒輪撓曲之情形時，亦可抑制齒輪之嚙合狀態之降低，並且抑制齒輪之磨耗，從而防止齒輪之強度下降。 齒輪機構12具備驅動齒輪15(第1齒輪之一例)與嚙合於驅動齒輪之小齒輪(第2齒輪之一例)20。驅動齒輪15具有複數個第1齒輪齒15a，該等複數個第1齒輪齒15a包含在將釣線捲取之旋轉方向旋轉時傳遞動力之第1正轉側齒面15b、及第1正轉側齒面15b之相反面之第1反轉側齒面15c。小齒輪20具有複數個第2齒輪齒20a，該等複數個第2齒輪齒20a包含嚙合於第1正轉側齒面15b之第2正轉側齒面20b、及於第2正轉側齒面20b之相反面與第1反轉側齒面15c對向之第2反轉側齒面20c。對向之第1反轉側齒面15c及第2反轉側齒面20c之至少一者具有防干擾部。
