The invention discloses a letter box device. The letter box device comprises a connecting arm, a frame body, a baffle, two connection column groups, a driving machine, two clamping claws, an iron sheltering device and two fixing arms, wherein the connecting arm is connected with a carrier; the frame body is fixed to the left end of the connecting arm, a second hole with the opening end towards left is formed in the frame body, the upper surface of the frame body is provided with a strip-like cavity, a first through hole is formed in right side of the position, below the strip-like cavity, of the second hole, and a vertical second through hole is formed in the portion, in the middle of the strip-like cavity, of the frame body; the baffle is fixedly installed at the left end of the frame body and penetrates rightwards into the second hole; the iron sheltering device is installed on the upper surface of the portion, on the right side of the first through hole, of the frame body; the two fixing arms are fixed to the left side face of the baffle. The letter box device is controlled by air pressure, the operation is convenient, the opening and locking of the clamping claws can be achieved by using one driving machine, the manufacturing cost is reduced, and meanwhile, clamping is safe and reliable.