A handle shaft support structure rotatably supports a handle shaft on a reel unit, and includes a boss portion, a roller type one-way clutch, and a pair of seal members. The boss portion is a cylindrical member that is detachably mounted to the reel unit. The one-way clutch includes an outer ring that is non-rotatably coupled to the inner peripheral surface of the boss portion, an inner ring that is arranged on the outer periphery of the handle shaft and is integrally rotatably coupled to the handle shaft, and rolling elements that are arranged between the outer and inner rings. The one-way clutch supports the handle shaft rotatably only in one direction. The pair of seal members are members that are arranged on the both sides of the one-way clutch to seal the one-way clutch.