A dual-mode input device includes a relative coordinate generator disposed in a casing for detecting motion of the casing and for generating relative coordinate information based on detected motion of the casing, and a processing unit. The processing unit includes a coordinate storing module for storing absolute coordinate information, an absolute coordinate generator for generating updated absolute coordinate information based on the relative coordinate information received from the relative coordinate generator and the absolute coordinate information received from the coordinate storing module, and for storing the updated absolute coordinate information in the coordinate storing module, and an output selecting module operable in one of a relative coordinate mode, in which the output selecting module outputs the relative coordinate information, and an absolute coordinate mode, in which the output selecting module outputs the absolute coordinate information.