A novel method for determining the carbonate ion contents in layered double hydroxides (LDHs) was demonstrated by FTIR spectrometry. Deconvolution using a curve-fitting technique was performed on the FTIR spectra of LDHs containing both carbonate and carboxylate ions in the interlayer. The contents of carbonate ion calculated from the FTIR spectra were in accordance with those obtained from the chemical composition analysis.