This paper introduces biohybrid microsystems actuated by cardiomyocytes, such as microcantilever, microrobot, and micropump. The microfabicated biohybrid microcantilever can measure the contractile force of self-organized cardiomyocytes. The microcantilever is made of a biocompatible PDMS substrate, using a simple microfabrication technique and a specially designed 3D micromolding aligner. The contractile force of the cardiomyocytes makes a bending displacement of the microcantilever. Conversely, from the displacement, we can estimate the contractile of the cardiomyocytes on the microcantilever. The bending motion of the microcantilever can be applied as a biohybrid actuator of microrobot. We have developed a novel method to fabricate a crab-like microrobot that can actuate for a long period under a physiological condition. The microrobot consists of three separate front and rear legs which have a shape of the microcantilever. The performance of our crab-like microrobot was measured at an average velocity of 100 mum/s, and the estimated total distance it traveled was 50 m for a one-week period. Finally, a micropump actuated by the self-beating cardiomyocytes is fabricated and the pumping performance is demonstrated.