Abstract: A three-component Stäckel model of the Galaxy, including the bulge, disk, and halo, is constructed. Parameter estimates of the potential are obtained as a result of fitting the model rotation curve to azimuthal velocities found from data on trigonometric parallaxes and spatial velocities of masers. The fitting method takes into account the measurement and natural dispersions of azimuthal velocities and uses an algorithm for excluding objects with excessive residuals. In order to obtain more uniform samples, the objects were divided into two groups: masers associated with high-mass star forming regions and masers of other types. A significant kinematic inhomogeneity of these groups was identified and taken into account: the azimuthal velocity dispersion is σ_0,1 = 4.3 ± 0.4 km s^–1 in the first group and σ_0,2 = 15.2 ± 1.3 km s^–1 in the second. After constructing the model of the Galactic-plane potential, it was generalized to the entire space under the assumption of the existence of a third quadratic integral of motion. When reconstructing the Galactic rotation curve in detail, the used algorithm gives an analytical expression for the Stäckel potential, which significantly simplifies the task of constructing the Galaxy's phase density model in the Stäckel approximation. In order to make the Stäckel model more realistic, one needs to develop methods of direct account of data on the vertical distribution of density in the Galaxy.