PURPOSE: To detect a head blank and a tail blank at the same time by specifying the kind of bar codes from the numbers of bar codes sandwiched between space parts and spaces according to the time of the space parts.

CONSTITUTION: Time data on blank parts are rearranged (sorted) in the decreasing order while their original places are stored. In this case, S35, S1, S34, S3, S2, and S33 are obtained. Two of the data are selected in order from the maximum value and the number of data present between the two data is counted. The data S31 and S1 are selected first and then the number of bar codes to be recognized is prescribed, so when it matches with the counted number, the place where the data close to the head in the original place between the two selected data is the head blank and the place where the other data is present is the tail blank. At this time, the kind of the bar codes having the matching counted number is specified as the kind of inputted bar codes.