All-solid-state micro-supercapacitors are acknowledged as a very promising class of microscale energy storage devices for directly integrating portable and wearable electronics. However, the improvement of electrochemical performance from materials to devices still remains tremendous challenges. Here, we demonstrate a novel and universal mask-assisted filtration technology for the simplified fabrication of all-solid-state planar micro-supercapacitors (MSCs) based on interdigital patterns of 2D pseudocapacitive MnO2 nanosheets and electrochemically exfoliated graphene film as both electrode and current collector, and polyvinyl alcohol/LiCl gel as electrolyte. Remarkably, the resulting MSCs exhibit outstanding areal capacitance of ~355 mF/cm2, which is among the highest values reported in the state-of-the-art MSCs. Meanwhile, MSCs possess exceptionally mechanical flexibility as high as ~92% of initial capacitance even at a highly bending angle of 180°, excellent cyclability with a capacitance retention of 95% after 3000 cycles, and impressive serial or parallel integration for modulating the voltage or capacitance. Therefore, our proposed strategy of simplified construction of MSCs will pave the ways for utilizing graphene and analogous pseudocapactive nanosheets in high-performance MSCs.