A laser radar apparatus includes a mixer 12 for converting the frequency of an electric signal outputted from a photodetector 11 into a baseband frequency by using a modulating signal generated by an oscillator 2. The laser radar apparatus carries out a coherent integral of the electric signal whose frequency has been converted by the mixer 12, and measures the quality of scatterers which exist in the atmosphere from a result of the integral. As a result, even when the S/N ratio of the light signal received by a receiving optical unit 8 is low, the laser radar apparatus can detect the quality of the scatterers.