PURPOSE: To obtain the data processor capable of maintaining the consistency of the outputted slips clearly at all times.

CONSTITUTION: Data of serial consecutive numbers to be set for each slip and updated for each output of the slip is recorded on a slip number gathering data recording part 31. An output control part 25 adds consecutive numbers on the slip based on the data recorded on the slip gathering number data recording part 31, and also adds the consecutive number of the slip on the data of the processing source to the slip when the slip is on the data after process. Thus, even when the slip is mixed after the slip output, the right time order of the slip and the order of data processing can be immediately confirmed on the slip.