Disclosed is an apparatus for multi-correcting a trajectory, the apparatus comprising a trajectory correcting unit in which a polygonal cam comprising a plurality of surfaces different in distance from a rotary center is rotatably installed between a dot sight or an optical signal and a firearm to adjust an angle between an optical axis of the dot sight or optical sight and a gun barrel axis of the firearm, wherein the trajectory correcting unit is installed to be movable in an axis direction, and coaxially provided with two or more polygonal cams to respectively set trajectory correcting angles corresponding to distances in accordance with calibers of a bullet and the kinds of bullet. With this, one dot sight or optical sight can be mounted to firearms using bullets different in the trajectory or firearms different in a caliber from one another, thereby enhancing equipment use efficiency.