A screw operation structure includes a screw-in portion that is capable of being mounted to a rear portion of a reel unit, a screw member, and an operation member. The screw-in portion includes an outer threaded portion, and a tubular portion that is integrally formed with the outer threaded portion. The tubular portion is formed such that the diameter thereof is larger than the inner diameter of the inner threaded portion of the screw member. In this configuration, the screw member is prevented from falling off of the screw-in portion by the tubular portion of the screw-in portion, which has a diameter that is larger than the inner diameter of the inner threaded portion of the screw member. In this manner, it is easy to mount an the operation member and the screw member in the reel unit.