Infrared Stark spectra for a Nylon 6 film were measured under electric fields from 0.99 to 1.5 MV/cm at 77 K using a sandwich-type cell with a BaF2/Al/Nylon 6/Al structure. The broad asymmetric infrared and Stark spectra observed for amide I (C=O stretch) were fitted with three components: 1637-cm(-1) band (beta-sheet structure), 1645- and 1663-cm(-1) bands (disordered hydrogen-bonded structures). The change in the dipole moment Delta mu between the ground and first excited vibrational states for amide I (beta-sheet structure) was determined to be 0.064 Df(-1), where f is a local field correction factor.