A fishing reel having a side cover that can be opened and closed in order to attach and detach a spool or the like. The fishing reel having the quick-opening side cover can be operated with one hand, in which a quick-opening system is employed such that a fisher can open the side cover by moving a lock by manipulating it with one hand. A grip of the lock can stay in the protruded state when the side cover is opened such that the fisher can close the side cover surely and securely, thereby preventing the side cover from being opened during fishing.