Disclosed is a method for controlling a light source and optical input device using the same. The light source controlling method includes setting a shutter ON time of an image sensor using a statistical value of an image obtained through the image sensor, and setting a light source ON time in accordance with the shutter ON time and turning on/off the light source and the shutter in response to the set light source ON time and the set shutter ON time.Thus, undesired consumption of electric power of the light source is prevented to increase energy efficiency by actively setting an ON/OFF period of the light source consuming the maximum electric current in the optical input device according to a shutter ON/OFF period. Further, availability of the light source and its electric current is enhanced by controlling the light source for the shutter OFF period and by allowing the light source to be used as a source for the data transmission.