A measuring instrument is provided with: a light emitting device (201) configured to irradiate light； a first light receiving device (211) and a second light receiving device (212) configured to receive return light of the irradiated light, which returns from an object (500) to be measured； and a calculating device (320) configured to calculate information regarding the object to be measured, on the basis of a difference between a sum signal and a difference signal, each of which is calculated from the light received by the first light receiving device and the light received by the second light receiving device. According to the measuring instrument, it is possible to remove unnecessary component, such as a body motion, and to accurately measure information on the object to be measured.
