A precipitation particle discriminator, comprising: an acquiring part configured to acquire horizontally polarized reception signals and vertically polarized reception signals by transmitting and receiving horizontally polarized waves and vertically polarized waves, respectively; a data processor configured to acquire information on radar reflective factors and information on differential reflective factors that are polarization parameters calculated based on the horizontally polarized reception signal and the vertically polarized reception signal; a distribution data generating module configured to generate distribution data indicative of relationship between the radar reflective factor information and the differential reflective factor information in a plurality of sampling ranges included in a discrimination target range, wherein the distribution data is a scatter plot where a first axis indicates the radar reflective factor, and a second axis indicates the differential reflective factor; a distribution data analyzing module configured to calculate an evaluation value used for discriminating a type of precipitation particles based on the distribution data, wherein the evaluation value is calculated using an approximated line of the distribution data, wherein the approximated line is a straight line, and the evaluation value is calculated at least using a slope of the straight line, and wherein the evaluation value is calculated further using an intercept of the straight line; and a discrimination processing module configured to discriminate the type of the precipitation particles existing in the discrimination target range based on the evaluation value. an acquiring part configured to acquire horizontally polarized reception signals and vertically polarized reception signals by transmitting and receiving horizontally polarized waves and vertically polarized waves, respectively; a data processor configured to acquire information on radar reflective factors and information on differential reflective factors that are polarization parameters calculated based on the horizontally polarized reception signal and the vertically polarized reception signal; a distribution data generating module configured to generate distribution data indicative of relationship between the radar reflective factor information and the differential reflective factor information in a plurality of sampling ranges included in a discrimination target range, wherein the distribution data is a scatter plot where a first axis indicates the radar reflective factor, and a second axis indicates the differential reflective factor; a distribution data analyzing module configured to calculate an evaluation value used for discriminating a type of precipitation particles based on the distribution data, wherein the evaluation value is calculated using an approximated line of the distribution data, wherein the approximated line is a straight line, and the evaluation value is calculated at least using a slope of the straight line, and wherein the evaluation value is calculated further using an intercept of the straight line; and a discrimination processing module configured to discriminate the type of the precipitation particles existing in the discrimination target range based on the evaluation value.