Pressure effects on the bilayers of polyoxyethylene type nonionic surfactant in water have been investigated by means of small- and wide-angle X-ray scattering. It has been found that the Krafft transition from the micellar phase to the lamellar gel phase (L-beta) is induced by pressure. By further pressurizing, the lamellar structural parameters, such as the repeat distance d and Caille parameter eta discontinuously decrease after taking a maximum. All the SAXS and WAXS results revealed that the L-beta phase is transformed into the higher-ordered lamellar crystal phase (L-c). On the basis of these observations, we have made the T-C and T-P phase diagrams.