Power electronics (PE) are an important technology for energy saving. However, PE apparatuses may emit electromagnetic interference (EMI) originated from the switching operation of power semiconductor devices. When EMI occurs in a system that includes many PE apparatuses, it is not easy to determine which one is the noise source. This paper applies high-speed sampling and signal-processing technologies to a field-programmable gate array (FPGA) to develop a frequency-analysis equipment that can judge the propagation direction of conductive EMI from 150 kHz to 30 MHz. Validity and usefulness of the proposed frequency analyzer is confirmed experimentally.