This paper describes an optimal design process of a permanent-magnet thrust bearing. The bearing consists of two sets of permanent magnet rings. One set is located inside the other. An axial displacement between the two sets creates an axial force, thereby achieving a thrust bearing function. In order to obtain an optimal design of the bearing where the required load capacity of bearing is achieved with the least magnet volume, we derived analytical design equations based on the equivalent current sheet (ECS) method. We considered two types of magnet arrays: axial arrays and Halbach arrays. Optimization is carried out for these two types. The results show that the Halbach array can achieve the load capacity requirement with smaller magnet volume than the axial array. We also found that there exists an optimal axial separation of rings for the axial array. The efficacy of the ECS method is verified against the results from three-dimensional finite element analyses and experiments. It is found that the Halbach array is more sensitive to the underlying assumptions of ECS method than the axial array.