An analytical procedure for evaluating the lateral drifting forces and moments between two ships in oblique waves by near-field method is presented in this paper. The velocity potential, including the hydrodynamic interactions are evaluated by a two-dimensional sink-source technique. Then the strip theory is applied to calculate the sectional force and the drifting forces and moments of the whole ships can be obtained by Simpson rules. Four components of the mean drifting force are obtained in which the relative wave term is dominant, whereas the Bernoulli quadratic component is secondary. The negative drifting force is observed at some frequency for the ship which is in the weather side of the wave. The lateral drifting force even occurs while the ships are in the head or following seas, which is consistent with the real physical phenomena at sea. The present technique offers the theoretical explanation for nonlinear phenomena between two ships in waves and will be helpful for the further practical study in random waves.