Disclosures of the present invention describe a device for measuring melatonin suppression induced by light source. The device consists of a light receiving unit, a pre-processor, a main processor, and a display unit. In the main processor, a first action spectrum generating unit is provided to convert a first light spectrum to first action spectrum, a second action spectrum generating unit is installed for converting a second light spectrum to second action spectrum, and a spectrum integrating unit is configured to produce a total action spectrum by integrating the first action spectrum with the second action spectrum. Therefore, the total action spectrum is evidenced can be used for describing the melatonin suppression power of both a short-wavelength light (<；460 nm) and the long-wavelength light by high correctness.
