A measurement method includes: a step of acquiring first observation point information; a step of acquiring second observation point information; a step of calculating a path deflection waveform at a third observation point; a step of calculating a path deflection waveform at a central position between the first observation point and the second observation point; a step of calculating a measurement waveform as a physical quantity at the third observation point; a step of calculating an amplitude coefficient at which a difference is minimized between the measurement waveform and a waveform obtained by multiplying the path deflection waveform at the third observation point by the amplitude coefficient; and a step of calculating, based on the path deflection waveform at the central position and the amplitude coefficient, an estimation waveform as a physical quantity at the central position.