Disclosed is a spectroscopic apparatus includes a laser irradiation device that receives an orthogonal code including a series of bits each having a first value or a second value, generates a control signal having a pulse that has a width shorter than a width of a bit section in the bit section corresponding to a bit having the first value, generates a pulsed laser beam having a pulse width shorter than the bit section using the pulse as a trigger, and irradiates an incident beam including the generated pulsed laser beam to a sample, and a detector that receives a detection signal generated from the sample and the orthogonal code, generates an orthogonal code signal of the same waveform as that of the incident beam, based on the orthogonal code, and demodulates a Raman signal, based on a correlation between the generated orthogonal code signal and the Raman signal.