PROBLEM TO BE SOLVED: To provide a measurement device to be mounted on a living body and a measurement method capable of measuring a prescribed action with a high degree of precision.SOLUTION: A measurement device 100 to be mounted on a living body includes: a conversion part for converting a variation in a distance from a prescribed region of a living body to an electric signal at a prescribed sampling period； a peak detection part for detecting a peak of the variation based on an electric signal to which the variation is converted by the conversion part； and a measurement part 53 for measuring the number of times or the time of a prescribed action based on the peak detected by the peak detection part. A ranging sensor 35, for example, can be used for the conversion part. Light is emitted from a light emitting part, the light reflected from the prescribed region is detected by a light receiving part, and the distance to the prescribed region is detected. An electric signal (voltage or current) according to the detected distance is converted with the prescribed sampling period.SELECTED DRAWING: Figure 5
