A spectrum measuring apparatus for measuring infrared, Raman and fluorescence spectra. The spectrum measuring apparatus includes an infrared source, a laser source, an infrared up-conversion object lens, an object lens, a dual color lens, an ocular, a narrow band filter, a visible light image capturing device and a sample pedestal. The infrared spectrum is measured by the infrared up-conversion object lens. The Raman and fluorescence spectra are measured by the object lens.