This paper deals with a mathematical model of the ship hydrodynamic forces in maneuvering motion at slow speed with large drift angle and tight turning. The model is structurally composed of several force elements and can be used to estimate the hydrodynamic forces on a ship in turning motion through the analysis of hydrodynamic forces in oblique motion without requiring turning experiments. The mathematical model was deduced from a vortex system, composed of a simple bound vortex system in/on the ship and a simple shedding vortex system around of the ship, based on the idea of slender body theory and the flow model of wing theory. The vortex wake around the ship in the former paper took into account the longitudinal flow, but in the present paper the 3 D cross-flow wake considers the lateral which is added to the former vortex wake. The trailing vortex containing the 3 D cross-flow wake effects the induced drag strongly in the longitudinal componet of ship hydrodynamic forces and most of the hydrodynamic forces are described by the vortex system in this paper, except frictional resistance and lift force due to asymmetric cross-flow.