Recently, there has been strong interest in printed robots and paper electronics. Printing is an adequate manufacturing method for the mass production; robots manufactured by printing can be low cost, rapidly creatable and easy to design. Paper is one of smart materials with high water absorbency and strength; it is easily mass-produced at low cost. Many inexpensive and flexible devices were created in paper electronics. Therefore, we propose paper mechatronics that merges printed robots and paper electronics. We used a commercial ink jet printer with water-based ink for self-folding of paper; the paper was folded automatically along the printed line to make the robot body. The paper robot was equipped with a printed electrothermal actuator that consists of epoxy resin covered by conductive ink. The epoxy resin was heated by Joule heat of the conductive ink under a driving voltage of 8 V. The self-folding of experimental paper robot took 15 minutes to construct the body and the robot demonstrated a locomotion at 6.5 mm per step.