To safely collect ores at the deep seabed by means of a simple structure.

Mining is carried out in accordance with instructions from a catamaran type mother ship 7 with a submarine operation vessel hanging down from the mother ship. Direct mining uses helical excavators 1, 4 equipped with cutters 5. Ores cut by the excavators are sucked up, together with seawater, are fed to a helical pump 13 in the operation vessel, and piled up. These operations are performed while being observed by means of lights 18 at the bottom of the ship and TV cameras 19. After mining is finished, equipment is raised to the mother ship and the ores are transferred onto the mother ship.