PURPOSE: To accurately detect change points of bar code by providing a differential means which differentiates the output signal of a reflective sensor and a bar code change point detecting means.

CONSTITUTION: Relating to a bar code reader in which bar code is read by a reflective sensor 11, a differential means 20 which differentiates the output signal of a reflective sensor 11 and a bar code change point detecting means 30 which detects points being about a half between the maximum and minimum values of the output signal of the differential means 20 as bar code change points are provided. The reflective sensor 11 consists of a light emitting diode and a phototransistor. The light emitting diode is connected between a DC power source and an earth point and the collector of the phototransistor is connected to the DC power source. The differential means 20 differentiates the output signal of the reflective sensor 11, and the bar code change point detecting means 30 detects points being about a half between the maximum and minimum values of the output signal of the differential means 20 as bar code change paints.