In this research, a micro sensor which can detect cavitation in a microchannel has been fabricated by using piezoelectric polymer thin film. P(VDF/TrFE) was used as the sensor material. We have applied integration by using the photolithography process to miniaturize sensors. We have succeeded in fabricating the micro-sensor whose thickness is 158μm. We have also succeeded in receiving waveform in the high frequency range. Thus the sensor would detect cavitation by using frequency analysis of bubbles collapse sound.