a complex transfer function calculator that calculates complex transfer functions from reception signals that are signals transmitted in a predetermined space from a transmission device including N transmission antenna elements, where N is a natural number greater than or equal to 2, and received during a predetermined period by M reception antenna elements, where M is a natural number greater than or equal to 2;

a variation component extractor that extracts living body information that is a variation component in the predetermined space;

a correlation matrix calculator that calculates a target correlation matrix from the living body information extracted by the variation component extractor;

a noise information storage that records a noise correlation matrix measured in the predetermined space;

a first headcount information calculator that calculates a threshold from the noise correlation matrix and calculates first headcount information by using, as a tentative value of the total number of living bodies that are present in the predetermined space, a total number of eigenvalues being greater than or equal to the threshold in the target correlation matrix;

a likelihood spectrum calculator that estimates a plurality of candidates for positions of the living bodies by a predetermined position estimation method, using the first headcount information and the target correlation matrix, and outputs likelihood spectra indicating likelihoods of the respective living bodies present in corresponding ones of the positions; and

a second headcount information calculator that estimates, by a predetermined method, second headcount information or positions from position information that is based on the likelihood spectra and can include the plurality of candidates for the positions, the second headcount information being a more accurate number of living bodies.