The present reel unit is a reel unit for a dual-bearing reel supporting a spool in a rotatable state. The reel unit includes a frame, a fishing rod attachment leg and a thinned part. The frame includes a first side plate, a second side plate disposed in opposition to the first side plate to enable the spool to be disposed between the first side plate and the second side plate, and a plurality of coupling members integrally formed with the first side plate and the second side plate to couple the first side plate and the second side plate. The fishing rod attachment leg is fixed to an outer surface of one of the plurality of coupling members. The thinned part has a box-like recessed shape and is formed on an inner surface, faced to the spool, of the coupling member to which the fishing rod attachment leg is fixed.