Abstract: A barcode reader is provided, able to turn on/off power or scanning function by itself according to use condition. The main structure thereof comprises a light source module, image sensor, information transferring device, and sensing device, wherein the sensing device is used to sense whether the light signal received by the image sensor changes during an interval of time and control on/off of the power or scanning function of internal elements in the barcode reader according to the change of the light signal. This way, not only the convenience in use can be raised, but also an object of saving energy and increasing lifetime of the barcode reader can be achieved.