PROBLEM TO BE SOLVED: To provide an optical device, a method and a program for measuring a fat thickness, which are capable of improving the precision of fat thickness measurement.SOLUTION: The device 1 for measuring the fat thickness includes: a control part 9 which activates a light-emitting part 5 in a predetermined cycle over a predetermined period of time with multiple amounts of luminescence and the identical amounts of the luminescence of two or more times in the period of time； a determination part 10 which obtains two or more amounts of the luminescence received by a light-receiving part 6 when the light-emitting part 5 is activated two or more times in the period of time with the amount of the luminescence identical to each of one or more amount of the luminescence to be determined out of multiple amounts of light received, and computes the differences with respect to each of two or more obtained amounts of the light received so that the multiple amounts of the light received corresponding to the multiple lights emitted in the period of time is determined to be valid when the differences computed with respect to each of the amounts of the luminescence to be determined are all under a threshold value； and a calculation part 11 which computes the fat thickness of a living body using the multiple amounts of the light received corresponding to the multiple lights emitted within the period of time when the validity is confirmed by the determination part 10.【課題】光学式の脂肪厚計測の計測精度を向上させる脂肪厚計測装置、脂肪厚計測方法および脂肪厚計測プログラムを提供する。【解決手段】予め決められた期間に予め決められた周期において、複数の発光量で、かつ、期間内に２回以上同一の発光量で発光部５を発光させる制御部９と、複数の受光量のうち１つ以上の判定対象の発光量の各々と同一の発光量で前記期間内に２回以上前記発光部５を発光させたときに受光部６が受光した２つ以上の受光量を取得し、取得した２つ以上の受光量各々について互いに差を求め、判定対象の発光量各々で求めた差が全て閾値内のとき、期間内に発光された複数の光に対応する複数の受光量を有効と判定する判定部１０と、判定部１０により有効であると判定されたとき、期間内に発光された複数の光に対応する複数の受光量を用いて生体の脂肪厚を求める算出部１１と、を備える脂肪厚計測装置１である。【選択図】図１
