A fat thickness estimating device includes a storage unit (180) that stores information indicating relationship between fat thickness and ratio of bioelectrical impedance in a first condition and bioelectrical impedance in a second condition, a measured impedance value acquiring unit configured to acquire a measured impedance value in the first condition of a target living body and a measured impedance value in the second condition of the target living body, and an estimation unit (193) configured to calculate a fat thickness value in the target living body based on the information and a ratio of the measured impedance value in the first condition and the measured impedance value in the second condition.
