An on-vehicle radar and a method of determining an axial deviation of the radar using stationary objects free of erroneous determination are disclosed. The amount of axial deviation of the radar is determined from the calculated stationary object line based on the distribution of stationary objects. In the case where such a factor for determining the calculated stationary object line as to reduce the calculation accuracy of axial deviation is detected in the distribution of stationary objects, the calculation of the amount of the particular axial deviation is canceled.