To provide an under floor storage system capable of storing objects in a wooden single house with carts running in crisscrossing directions in spaces among floor struts.

Guide rails 1 are laid in spaces running among floor struts 71. Two, right and left pallets are disposed on the guide rail 1 in the longitudinal direction. Carts 11, 12 and laterally transfering carts 22, 23 are reciprocated with a driving motor 13 to move the pallet (storage box) intermittently in a mass game system. When a specific holding box is called with a controller, holding boxes are moved sequentially. When the specific box comes to an entrance, the box is raised above the floor with a lift apparatus 30. When stowage or takeout is over, the storage box is lowered with the lift apparatus 30 onto the guide rail 1.