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An optical probe current sensor module using the Kerr effect has been fabricated and applied to switching current measurements for IGBT used for the DC-DC converter and the DC-AC inverter of EV/HEV. Since the sensor module using the Kerr effect of the single domain exchange-coupled magnetic thin film utilizes magnetization rotation only, the Barkhausen noise due to domain wall pinning can be excluded. The current sensor consists of a Laser-diode, a polarizer, a Fe-Si/Mn-Ir exchange-coupled film, a quarter-wavelength plate, a Glan-Laser polarizer, PIN Photodiodes and a differential amplifier. The optical probe current sensor has a current measurement range of ±60 A and a frequency range of DC - 200 kHz. The switching current of IGBT has been measured by it.