PURPOSE: To eliminate an erroneous measurement by executing an exact counting by calculating a walking speed of a pedestrian and human body width of the pedestrian by use of two sets of light emitting devices and photodetectors, and counting, displaying and recording the number of the pedestrian sensed by a decision of the obtained human body width.

CONSTITUTION: When a pedestrian walking along a path passes through between light emittig devices 1a, 1b and photodetectors 2a, 2b, optical beams La, Lb placed at a distance l are cut off, therefore, a cut-off pulse waveform is obtained n the photodetectors 2a, 2b. The distance l is held at a smaller value than the minimum value considered as human body width, for instance, 10cm. The outputs of the photodetectors 2a, 2b are inputted to a count-processing part 3, and are time-counted by a clock pulse from a timing generator 5. The processing part 3 calculates the walking speed of the pedestrian and the human body width of the pedestrian detects the passing of the pedestrian by the decision of the obtained human body width, counts the sensed number of the pedestrians at every section provided by a unit time or an external condition, sums it up, and displays and records it. In this way, the erroenous measurement can be prevented by executing the exact counting.