The reel unit includes a reel body that accommodates a variety of mechanisms therein and a T-shaped rod attachment leg that extends diagonally frontward and formed integrally with the reel body. The reel body includes a body member having an accommodation space in the interior thereof that opens to a side, and a lid member detachably mounted on the body member to cover the opening of the body member. A reduced thickness portion is formed in an upper rear portion of the reel body, where the rod attachment leg connects the reel body. The reduced thickness portion has a peripheral rim portion and a recessed portion that is further recessed from the peripheral rim portion. The cover member is mounted to cover the rear lower portion of the reel body in order to cover at least the peripheral rim portion of the reduced thickness portion.