In a method, whether there is a first bar having a width and located at at least one of both ends of a first black and white pattern is determined. The width of the bar is greater than a maximum width of a second bar. The maximum width of the second bar appears in a second black and white pattern assuming that the black and white pattern is part of the first barcode. The first black and white pattern is determined as readout data of the second barcode when it is determined that there is the first bar having the width greater than the maximum width of the second bar and located at at least one of both ends of the first black and white pattern.