In accordance with an embodiment, a componential analysis method includes dividing a sample structure into at least a first layer to be analyzed and a second layer located closer to a surface layer of the sample than the first layer, applying, to the sample, laser lights of first and second wavelengths respectively corresponding to the depths of the first and second layers, detecting Raman scattered lights respectively obtained from the sample by the application of the laser lights and then outputting first and second Raman signals, spectrally processing the first and second Raman signals to acquire first and second Raman spectrums, acquiring a differential spectrum by subtracting the second Raman spectrum from the first Raman spectrum, and analyzing the differential spectrum.