A reciprocating mechanism 8 includes a first supporting member 24, a second supporting member 25, and a biasing member 26. The worm shaft 20 includes a shaft portion 20a, a first shaft supporting portion 20b having a spherical portion 20e formed in a convex spherical shape at a distal end, and a second shaft supporting portion 20c. The first supporting member 24 includes a first bottom portion 24a abutting the spherical portion 20e. The second supporting member 25 includes a second bottom portion 25a abutting a distal end of the second shaft supporting portion 20c. The biasing member 26 biases at least one of the first supporting member 24 and the second supporting member 25 in an axial direction.本發明提供一種釣具捲線器的往復移動機構，於釣具捲線器的往復移動機構中，即便對蝸桿軸賦予相對較大之預壓之情形時，仍可抑制蝸桿軸之轉矩之上升。往復移動機構8具備第1支持構件24、第2支持構件25及推壓構件26。蝸桿軸20具有軸部20a、於前端具有形成為凸球面狀之球面部20e之第1軸支持部20b及第2軸支持部20c。第1支持構件24具有抵接於球面部20e之第1底部24a。第2支持構件25具有抵接於第2軸支持部20c之前端之第2底部25a。推壓構件26將第1支持構件24及第2支持構件25之至少一者向軸向推壓。
