The invention discloses a device and a process for largely and industrially preparing biochemical natural gas by utilizing organic wastewater. The device mainly comprises a reaction pot body (1) the upper end of which is opened and the inside of which is provided with a cavity, and is characterized in that the bottom of the reaction pot body (1) is provided with an intake area (2) communicated with the cavity; the inner side of the open end of the reaction pot body (1) is provided with a gas-collecting hood (5); the side wall of the reaction pot body (1) is also provided with a drain pipe which is communicated with the cavity by the open end of the reaction pot body (1), wherein the opening of the drain pipe faces upwards; and the inside of the reaction pot body (1) is also provided with a reaction area (4) and an activated sludge bed (3) in sequence from top to bottom. The device has very simple integral structure and collects methane gas generated by reaction by adopting the gas-collecting hood, thereby effectively avoiding the defect that an ideal structure size is difficult to design due to the fact that the angles of the baffle and the backflow seam, the opening width and the like of the traditional reactor are influenced by the concentration and the variety of the wastewater.