The invention discloses a board corner polishing device and relates to the technical field of board machining. Specific to the problems that manual operation is conducted during existing chamfer polishing of wood boards, thus polishing efficiency is low, much dust is produced during manual operation and is bad for the health of workers, and meanwhile, the boards need to be fixed manually during manual polishing operation, the following scheme is provided that an installation plate is included; a holding table is installed at the top of the installation plate; a driving mechanism is arranged above the holding table; a fixed device is arranged below the driving mechanism; and four polishing devices are arranged on the outer circle of the holding table in an array, are arranged at the top ofthe installation plate slidably and are connected with the driving mechanism. According to the board corner polishing device, the distance from a polishing belt to the holding table can be adjusted conveniently, thus boards of different sizes can be polished conveniently, the boards are also pressed and fixed during close polishing, time and labor are saved, no manual operation is needed, and health of workers is facilitated.