1. An optical information reading device, comprising: a computation means for adding widths of n elements (n≧2) containing a bar and a space 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 the module numbers of the 2- through n-element added widths; an extraction means for narrowing down the target characters to extract a candidate character wherein the target character is that each module number of the 2- through n-element added widths derived by said computation means is an integer with an error equal to or less than 1; and a search means for comparing the candidate character, having the module numbers of the 2-through n-element added widths extracted by said extraction means, with the expected value character for evaluating the candidate character to search for an expected value character with the strongest correlation to the candidate character.