A spinning reel spool coupling structure has a pin insertion portion (8d), an anti-rotation pin (50), a retainer (51), and an anti-rotation groove (24c). The pin insertion portion (8d) has a through hole (8c) passing through the spool shaft (8). The anti-rotation pin (8d) includes a first anti-rotation portion (50a), a fitting portion (50b), and a second anti-rotation portion (50c). The fitting portion adjoins the first anti-rotation portion (50a), and fits into the pin insertion portion. The second anti-rotation portion (50c) extends from the fitting portion (50b) and has a diameter greater than that of the pin insertion portion. The retainer member (51) prevents the anti-rotation pin from being detached from the spool shaft (8), is disposed on an outer peripheral side of the first anti-rotation portion, and has an axial length such that the retainer member contacts the spool shaft (8). The anti-rotation groove (24c) is formed to extend in a direction substantially perpendicular to a length of the spool shaft, and engages the second anti-rotation portion.
