There is provided a substance detecting device emits first invisible light to the inside and the outside of a detection region of a substance, changes an emitting direction of the first invisible light inside and outside the detection region, receives third invisible light which is passing light of the first invisible light through the reference cell in which a detection target substance is stored, outside of the detection region, and adjusts a temperature of the first invisible light and controls the wavelength of the first invisible light based on the wavelength characteristics of the third invisible light.