Abstract: A robot system includes a robot that includes a hand and a robot main body. The hand is mounted to the robot main body and is configured to suck a box material. The robot main body assembles the box material sucked by the hand while moving the box material in a predetermined direction. A first fixed folding member accepts an inside flap of the box material so as to fold the inside flap and render the inside flap into a bottom surface or an upper surface of the box material. A second fixed folding member accepts an outside flap of the box material so as to fold the outside flap and render the outside flap into the bottom surface or the upper surface of the box material.