We present a novel MEMS-based power generator using activation of cardiomyocytes. Cardiomyocytes are cultured on the MEMS fabricated lead magnesium niobate-lead titanate (PMN-PT) single crystal diaphragm, directly and the mechanical stress induced by contraction forces from cardiomyocytes is conversed into electrical power. This PMN-PT single crystal diaphragm has one-side interdigitated electrode design, which makes it possible that an external stress applied to the diaphragm results in output charge or voltage by piezoelectric effect. After 4 days of in vitro culture, the output voltage from this cell-hybrid MEMS generator was measured successfully. We show the possibility that our device can be used as an alternative micropower source for micro/nanorobots or the micro implantable systems, and can be applied to study a quantitative understanding of the mechanism of heart failure also.