1. An optical information reading device, comprising: a computation means for adding widths of 2 elements through n elements, the 2 elements containing a bar and a space that are adjacent within one character, wherein n is greater than 2, the n greater than 2 elements containing two or more bars and one or more spaces and one or more bars and two or more spaces that are adjacent within one character to derive respective 2- through n-element added widths and for converting each of the 2- through n-element added widths into the module number for one character to derive an actual measurement value of the module numbers of the 2- through n-element added widths; an extraction means for narrowing down target characters wherein each of errors between the actual measurement value and an ideal value of the module number for all the 1-element and the 2- through n-element added widths derived by said computation means is equal to or less than 1, to extract candidate characters; and a search means for searching the one candidate character having the minimum of the summed errors as the readout decode result.