An estimation method according to the present disclosure includes: extracting, from a plurality of calculated complex transfer functions, living body components respectively corresponding to N reception antenna elements and affected by a living body; calculating a correlation matrix based on the extracted living body components respectively corresponding to the N reception antenna elements; computing one or more eigenvalues of the calculated correlation matrix; estimating a credibility of an estimation result of estimating the position or the direction of a living body in a target space, using the one or more computed eigenvalues and living body count information indicating a value indicating a total number of living bodies in the target space; and estimating the position or the direction of the living body via a predetermined method, based on the correlation matrix, according to the credibility of the estimation result.