An impact elastic wave test is conducted to measure propagating waves in a pipe to be examined, a frequency spectrum of the propagating waves is analyzed, and at least a spectral area value in a first frequency region and a spectral area value in a second frequency region of the frequency spectrum are evaluated, thereby determining a type of a deteriorated state of the buried pipe. A correlation relationship between a parameter obtained from a force-deformation relationship indicating a relationship between a force externally input to a sample pipe and a deformation of the sample pipe due to the force, and impact elastic wave test data obtained by conducting an impact elastic wave test with respect to the sample pipe is previously obtained, an impact elastic wave test is conducted with respect to a pipe to be examined to collect impact elastic wave measurement data of the pipe to be examined, and the actually measured impact elastic wave measurement data is evaluated based on the correlation relationship, thereby quantitatively determining a degree of deterioration of the pipe to be examined.