An image printing method and apparatus which can detect the edge of a printing medium on which a barcode is written, whilst reading the barcode, using one sensor unit. The apparatus includes a sensor unit (310) sensing the barcode and generating a sensing signal. A first counting unit (320) counts the sensing signal to generate a first count value when the value of the sensing signal is first changed from a high value to a low value. A second counting unit (330) counts the sensing signal of the barcode concurrently with the first counting unit to generate a second count value which is initialized whenever the value of the sensing signal is changed. A detecting unit (340) detects the edge of the printing medium based on the first and second count values of the first counting unit and the second counting unit. A reading unit (350) reads the barcode based on the second count value of the second counting unit.