This paper presents a method for calculating eddy current loss in permanent magnets of a surface permanent magnet (SPM) motor based on electric and magnetic networks. First, an electric network model to calculate the eddy current loss is indicated. Then, to find the resistivity of a Nd-Fe-B magnet, eddy current loss in the magnet is measured by using a test core. Next, a reluctance network analysis (RNA) model of the SPM motor considering the rotor rotation is presented. The eddy current losses in the magnet of the SPM motor from no load to full load conditions are calculated by the RNA model and electric network model. The eddy current losses calculated by the proposed model agree well with the ones obtained from three-dimensional finite-element analysis.