The utility model discloses a board-separating device which comprises a support, wherein a movable portion capable of moving vertically is respectively arranged on two opposite sides of the support, guide rods are arranged laterally on the movable portions, second guide grooves for insertion of two free ends of the guide rods are respectively vertically formed in the rack, through grooves are formed in the movable portion, adjusting portions are inserted inside the through grooves, inner free ends of the adjusting portions are support heads, outer free ends of the adjusting portions extend out of the through grooves, adjusting grooves are vertically formed in the rack, a side wall close to the inner wall and a side wall close to the outer wall of each adjusting groove comprise corresponding upper groove sections, slant sections and lower groove sections, wherein the two slant sections incline from top to bottom from inside to outside, the two slant sections are arranged in a stagger mode, and the slant section at the outer side is higher than the slant section at the inner side. The board-separating device is simple in structure, flexible and adjustable, and capable of providing a novel operation method for operation of separating the board with a brick.