PURPOSE: To achieve an accurate speed measurement of a vehicle to be measured automatically regardless of measurement environment or personnels.

CONSTITUTION: A doppler signal which indicates a relative speed with a vehicle to be measured is extracted by a doppler radar. A doppler signal is passed through a band-pass filter by a band-pass filter, thus obtaining a doppler signal which indicates that the relative speed is nearly equal. When the doppler signal which is passed through the band-pass filter continues for a specified amount of time, it is regarded that the vehicle to be measured is driving at nearly equal speed, thus enabling a command to be sent to a printer and the speed of the vehicle to be measured to be printed.