Langmuir-Blodgett (LB) multilayers of a novel azobenzene derivative were fabricated and studied by polarized transmission Fourier transform infrared spectroscopy. The dichroism in two perpendicular polarizations revealed that there exist two types of hydrogen-bonded carboxyl groups, which are orientated in planes perpendicular to each other, forming a two-dimensional intermolecular hydrogen-bonded structure in the LB film.