Stability and deformation of the seabed in response to ocean wave loading is an important consideration in the design of near-shore structures. Using a procedure similar to Ishihara's analysis (1983) the quasi-static behavior of loosely deposited sandbed under the action of standing wave is examined. To describe the characteristics of the cohesionless sand deposits, the constitutive equations are derived within the framework of bounding surface plasticity theory along with a non-associated flow rule possessing the ultimate (critical) state and the compact state, which is recently introduced by the authors. In the present study, the influence of the wave amplitude and the wave length for a broad range of void ratio of seabed sand to wave motion are discussed.