We use cell traction force (CTF) to self-fold flat microplates into diverse three-dimensional (3D) cell-laden microstructures (Figure 1). Cells were selectively cultured onto the flat microfabricated plates. Immediately after detaching the plates from the glass substrate, the plates were lifted and folded up into the 3D microstructures due to the CTF caused by stretched cells that adhered between two plates. We achieved precise folding angles between the folding microplate and glass substrate by producing a flexible joint between the plates. Using the microplates with the flexible joint, we also achieved batch process of self-folding 3D cell-laden microstructures. In addition, we succeed to produce micro-flapping structures using cardiomyocytes as an actuator.