A fishing spinning reel includes a flat reel body, two side covers, and a driving unit. The reel body is made of metal, and has a plurality of mounting holes formed through the reel body. Each of the mounting holes has two open ends at two opposite sides of the reel body. The side covers are made of a plastic material, are disposed respectively on the opposite sides of the reel body, and are interconnected to clamp the reel body therebetween so as to define an accommodating space among the reel body and the side covers. The driving unit is disposed within the accommodating space.