A sputtering device for deposition of multicomponent high-entropy metallic coatings with increased protective properties is proposed. The device is based on magnetron sputtering and hollow cathode effect with the sputtering target in the form of a composite rod. Application of the sputterer includes deposition of coatings onto the inner surface of low diameter pipes (above 4 cm). In the present work, a mathematical model is developed for the sputterer that describes mass transfer of the sputtered material and allows calculating mole fraction distribution of the coating components depending on the surface coordinates, composite rod-like target configuration, and geometrical parameters of the main construction elements as well. Formulation of the model starts with consideration of the physical background and the sputterer features. Mole fraction equations are derived from cosine distribution of sputtered atoms and Gaussian-type alterations of the sputtered flux due to scattering on the working ambient particles. First, the mole fraction distribution is obtained for no-scattering conditions and cross-section geometry and the rod made of two half cylinders. After adding scattering factors, the model is validated and adjusted by comparison with experimental data. And as the most promising for application, the rod configuration in the form of longitudinal sequential discs set is considered. The developed model allows detailed designing of the sputterer configuration and determining deposition conditions of high-entropy metallic coatings with specified compositions.