A design method of cloth-structured magnetic device was obtained and it made clear the optimized relation between amorphous fiber and conductive fiber in size. At the design method, inductance, equivalent resistance and quality factor of cloth-structured magnetic devices were obtained analytically. It was close agreement between the measured value and the computed one. Furthermore, the stray capacitance of the device was estimated from the analysis of equivalent circuit. The analysis showed very small capacitance in the cloth-structured device.