Disclosed herein are an optical pen mouse capable of magnifying a displayed object and a method of magnifying a displayed object using the same. The optical pen mouse includes a magnification setting unit and a microcomputer. The magnification setting unit inputs a magnification (M) so as to adjust a size of an object to be displayed on the monitor of a computer. The microcomputer calculates input coordinate values (X,Y) (a horizontal coordinate value, a vertical coordinate value) based on an electrical signal from the light receiving unit, and, when the magnification (M) is received from the magnification setting unit, calculates display coordinate values (X′,Y′) based on the input coordinate values (X,Y) and the magnification (M), converts the calculated display coordinate values (X′,Y′) into a coordinate data code, and outputs the coordinate data code.