Space exploration is conducted to elucidate the origin of the solar system. Currently, satellites are often used, but rover exploration is also being considered to obtain subsurface information. Swarm robotic exploration using multiple small rovers is also being studied. Excavation is necessary for subsurface exploration. However, it is difficult for a single small rover to excavate a deep area because of its lightweight and the excavation resistance of the ground. Therefore, we propose a method of excavation by combining and extending multiple small rovers.