When a motor is running under a load condition, it is difficult to analyze and measure the diverse types of loss occurring in the motor. To address this problem, the analysis and the measurement methods that assess the losses in a motor under a load condition are proposed in this paper. In high power density types of motors, eddy current loss is the major type of loss. A three-dimensional finite element method has been used for the analysis of the eddy current loss, which requires the much time and effort in the design process. To solve this problem, in this study we propose an analytic method that can be used for the analysis of the eddy current loss. The proposed loss analysis and measuring methods for a permanent magnet motor under a load condition are validated using a prototype.