A method of the invention reads a bar code based on bar-code data obtained by scanning the bar code with light. The method includes the steps of a) obtaining bar-code data, b) obtaining a sum of bar-data widths with respect to a predetermined number of bar data provided in at least one of a preceding portion and a following portion of the bar-code data, c) repeating the steps a) and b) once to obtain another sum, and d) making a comparison of the sum with another sum. The methods further includes a step of accepting the bar-code data as valid data when a result of the comparison satisfies a predetermined condition.