The present reel unit (1) is a reel unit for a dual-bearing reel (100) supporting a spool (12) in a rotatable state. The reel unit (1) includes a frame (5), a fishing rod attachment leg (10) and a thinned part (11). The frame (5) includes a first side plate (8), a second side plate (9) disposed in opposition to the first side plate (8) to enable the spool (12) to be disposed between the first side plate (8) and the second side plate (9), and a plurality of coupling members (14) integrally formed with the first side plate (8) and the second side plate (9) to couple the first side plate (8) and the second side plate (9). The fishing rod attachment leg (10) is fixed to an outer surface (15b) of one of the plurality of coupling members (14). The thinned part (11) has a box-like recessed shape and is formed on an inner surface (15a), faced to the spool (12), of the coupling member (14) to which the fishing rod attachment leg (10) is fixed. Furthermore, a dual-bearing reel comprising such a reel unit (1) and a method of manufacturing the such a reel unit (1) are also disclosed.
