This paper presents a semi-analytical finite element method to derive the slot leakage inductance of rotating electrical machines with double-layer windings. The proposed method combines the lower computational burden of analytical equations and the accuracy/flexibility of the finite element method. Moreover, only a two-dimensional finite element simulation of one slot pitch is required. This method can be applied to an arbitrary slot geometry and winding configuration. The slot leakage inductance of a 12-slot and 10-pole tooth-coil-winding permanent-magnet synchronous machine was evaluated through the proposed method and only finite element method simulation. Three different slot shapes with vertical and horizontal coil sides arrangements were considered in the analysis. The results show that the semi-analytical method provides accurate results and low computational times.