The theory developed in reference [1] has been extended to thicker films. The compensation equation and current equation are derived for superconducting films in a magnetic field, on the basis of a model which assumes the energy-gap function to be constant over the whole film and by means of Schrieffer's technique. The equations obtained are applied to discuss the influence of an external magnetic field on the superconducting properties of a metallic film and its transition changes. The formulas for determining energy-gap, magnetic moment, and critical fields Hc, H(c1) and H(c2) which correspond respectively to equilibrium transition and to boundaries of supercooled and superheated region, are given. All the expressions have been reduced to the well-known results of the Ginzburg-Landau theory in the local limit and to those of reference [1] in the thin film limit. Non-local effects in the general case have been discussed in detail.