We verified the applicability of a fiber-optic sensor to deformation monitoring of the seal equipped with an air cushion vehicle such as a surface effect ship (SES). The seal is a membrane structure made of an elastomeric material. It is difficult to measure deformation or vibration of the membrane structures by using a sensor which is fixed on it. In laboratory tests, we could measure strain-rate of the seal material subjected to cyclic loading by using the fiber-optic sensor adhered to it. Then, in monitoring tests of a small model of the seal with the sensors, frequency or amplitude of vibration was changed according to the velocity of water flow or the length of the bottom in water. In this paper, we described the results of these tests and showed the good applicability of the fiber-optic sensor to measure the response of membrane structures which have elastomeric properties.