The present invention discloses a board cutting device, which comprises a base frame, a push stem, a blade, a first one-direction driving mechanism, and a second one-direction driving mechanism. One end of the push stem is linked with the base frame, and there is a handle at the other end. The blade is attached on the push stem and is able to simultaneously revolve with the push stem relative to the base frame. The middle portion of the blade is a protruded cutting arc. The first one-direction driving mechanism is utilized to adjust the angle between the push stem and the blade automatically, and the second one-direction driving mechanism can be utilized to control the automatic positioning of the downward cutting blade. Therefore, the blade can avoid arbitrary departing from the prep board and the device is able to achieve the object of better manipulation, less strenuous effort, and more accurate cutting.