A distance measuring device for a vehicle emits electromagnetic waves forward for a scan both in horizontal and vertical directions. It is judged from received light whether or not the distance to a detected object is within a specified preset range. If the distance is found to be within this range and if at least two specified conditions are satisfied, this object is regarded as a vehicle in the subsequent scans and a flag is set to this effect. One of these two conditions requires this object to have been judged as being a front going vehicle continuously over a time longer than a preset minimum time length. The second condition is that the difference between the distance to this object measured by a scan that is the highest or nearly the highest in the vertical direction and the measured distance to a front going vehicle corresponding to the object is within a predetermined range.