The steady driven flow of an incompressible viscous fluid in a two-dimensional square cavity is numerically calculated using the finite difference method proposed by B. P. Leonard. The governing Navier-Stokes equations in the streamfunction-vorticity form are discretised on the nonuniform staggered mesh by the third order scheme, and the resulting equations are iteratively solved. The calculation is performed for the cavity flow at Reynolds numbers up to 5 multiplied by 10**4. The results obtained are confirmed to be consistent with those which have been found using known second order methods. When the Reynolds number increases above 10**4, the corner separation flow regions continue to gradually extend, and correspondingly each eddy contained in the corner regions is deformed.