The invention discloses a letter box device. The letter box device comprise a main seat body, a first sliding connecting cavity is formed in the main seat body, guiding connecting grooves are symmetrically formed in the inner walls of the left and right sides of the first sliding connecting cavity, a second sliding connecting cavity is formed in the position, located in the main seat body, of thelower side of the first sliding connecting cavity, and a through opening is formed in the part between the first sliding connecting cavity and the second sliding connecting cavity in a communicating mode. A transmission connecting cavity is formed in the position, located in the main seat body, of the upper side of the first sliding connecting cavity, first cone side wheels penetrating into the transmission connecting cavity are rotatably connected into the part between the guiding connecting grooves on the left and right sides and the transmission connecting cavity in a matched mode, and second cone side wheels separately connected with the first cone side wheels on the left and right sides in a power fit mode are fixedly arranged on a transmission connecting shaft in a left-right symmetry mode. A setting frame is connected into the first sliding connecting cavity in a sliding fit mode, and the setting frame is internally provided with a smoothing device.