In estimation of a future state of a first product (an estimation-target individual), a first estimated extrapolation value is calculated from data on a past side of data relevant to the first product, and a second estimated extrapolation value is calculated from data relevant to a second product (a same-type different-individual of the estimation-target individual) that is different from the first product. A synthesis ratio between the first estimated extrapolation value and the second estimated extrapolation value is decided from data on a present side of the data relevant to the first product, and an estimation value is calculated by performing synthesis between the first estimated extrapolation value and the second estimated extrapolation value based on the decided synthesis ratio.