A spectrum measuring device including a ribbon element, a light detection element, and circuitry. The ribbon element includes a first light reflector including a plurality of first light reflection surfaces configured to be translated in an out-of-plane direction, and a second light reflector including a plurality of second light reflection surfaces that are fixed. The circuitry supplies a drive signal to the ribbon element in such a manner that a change of a displacement amount difference between the first light reflection surfaces and the second light reflection surfaces corresponds to a predetermined frequency; and acquires the light quantity data detected by the light detection element at a predetermined sampling frequency.