Disclosed herein is a method for processing image data of an optical mouse. In the method for processing image data of an optical mouse, direction and size values of motion vectors which are image data consecutively inputted from an image pixel array are filtered with respect to X and Y axes by a filter. A predetermined number of motion vectors converted by and outputted from the filter are accumulated, and the accumulated values are mapped to conversion values to attenuate noise components and amplify directionality of the motion vectors depending on a speed of the optical mouse by a mapper. The values mapped by the mapper in a plurality of pipes are stored, and a value obtained by adding the plural stored values to each other and dividing the added result value by a conversion factor is transmitted to a personal computer (PC) interface such as a Universal Serial Bus (USB) or PS/2. Accordingly, the present invention is advantageous in that it minimizes noise components of the optical mouse, and consequently ensures the unnatural movement of a cursor on a PC screen.