Fusion science and technology of electromagnetic field is proposed here to obtain a higher efficient and downsizing electrical motor drive system, for example. Motor drive system does not consist of only one technology such as electrical motor, control, power electronics, material, and production process. “Electromagnetic energy apparatus,” “electromagnetic field application,” and “electromagnetic material” are considered to be related by a transfer of “thing.” Each component requires multitime for power electronics, multiphysics, and multiscale, respectively. They should be considered to be a fusion science and technology such as electrical engineering, material, electromagnetic field, fluid dynamics, or so. Hence, they are called first-class fusion. The relation among the apparatus, the application, and the material is a relation of “purpose” and “means.” The purpose introduces what to make, and the means introduces how to make. So they are called second-class fusion. It is usually difficult, and a lot of time is needed to learn plural department at the same time in the conventional study system. Therefore, some special study system may be required for them.