A spectroscopic analysis apparatus comprising: a main body; a light projecting unit configured to project infrared light to a steel strip in motion; a light receiving unit configured to receive, as reflected light, the infrared light reflected by a surface of the steel strip; an output unit configured to calculate either or both of a composition and a composition ratio of the surface of the steel strip using the reflected light received by the light receiving unit; wherein the light projecting unit, the light receiving unit and the output unit are comprised within the main body; and a position adjustment mechanism for adjusting position of the main body of the apparatus, wherein the light receiving unit includes: a separator configured to separate the reflected light into s-polarized light and p-polarized light; a detector for s-polarized light configured to detect s-polarized light obtained through the separation by the separator and output an electric signal indicating an intensity of the s-polarized light to the output unit; and a detector for p-polarized light configured to detect p-polarized light obtained through the separation by the separator and output an electric signal indicating an intensity of the p-polarized light to the output unit, the output unit is configured to: calculate an absorbance based on a ratio between the intensities of the s-polarized light and the p-polarized light using the electric signals output from the detector for s-polarized light and the detector for p-polarized light; and calculate either or both of the composition and the composition ratio of the surface of the steel strip using an intensity of the absorbance at any desired wavenumber, and the position adjustment mechanism includes a two-axis adjustment mechanism for a liftoff adjustment and rotation and tilt adjustments between the steel strip and the main body of the apparatus. a main body; a light projecting unit configured to project infrared light to a steel strip in motion; a light receiving unit configured to receive, as reflected light, the infrared light reflected by a surface of the steel strip; an output unit configured to calculate either or both of a composition and a composition ratio of the surface of the steel strip using the reflected light received by the light receiving unit; wherein the light projecting unit, the light receiving unit and the output unit are comprised within the main body; and a position adjustment mechanism for adjusting position of the main body of the apparatus, wherein the light receiving unit includes: a separator configured to separate the reflected light into s-polarized light and p-polarized light; a detector for s-polarized light configured to detect s-polarized light obtained through the separation by the separator and output an electric signal indicating an intensity of the s-polarized light to the output unit; and a detector for p-polarized light configured to detect p-polarized light obtained through the separation by the separator and output an electric signal indicating an intensity of the p-polarized light to the output unit, a separator configured to separate the reflected light into s-polarized light and p-polarized light; a detector for s-polarized light configured to detect s-polarized light obtained through the separation by the separator and output an electric signal indicating an intensity of the s-polarized light to the output unit; and a detector for p-polarized light configured to detect p-polarized light obtained through the separation by the separator and output an electric signal indicating an intensity of the p-polarized light to the output unit, the output unit is configured to: calculate an absorbance based on a ratio between the intensities of the s-polarized light and the p-polarized light using the electric signals output from the detector for s-polarized light and the detector for p-polarized light; and calculate either or both of the composition and the composition ratio of the surface of the steel strip using an intensity of the absorbance at any desired wavenumber, and calculate an absorbance based on a ratio between the intensities of the s-polarized light and the p-polarized light using the electric signals output from the detector for s-polarized light and the detector for p-polarized light; and calculate either or both of the composition and the composition ratio of the surface of the steel strip using an intensity of the absorbance at any desired wavenumber, and the position adjustment mechanism includes a two-axis adjustment mechanism for a liftoff adjustment and rotation and tilt adjustments between the steel strip and the main body of the apparatus.