In a band saw, it is intended that a so-called blade drift is corrected and straight line cutting of an object is easily performed. Further, an accurate correction is realized by a simple operation. A cutting auxiliary device in the band saw in accordance with the present invention is a device used to correct a shift of a cutting line when the cutting line is shifted from a straight line in the band saw for cutting a work by using a flexible steel band. The cutting auxiliary device in the band saw has a working board having a board face for performing an operation for cutting the work and equipping an edge port plate for passing the flexible steel band on the board face; a working board support portion for supporting the working board so as to be horizontally rotated with the flexible steel band as a center; a laser projector attached to a band saw main body side and projecting a laser beam so as to be overlapped with the shifted cutting line when the work is straightly cut by the flexible steel band on the working board and the cutting line is shifted from the straight line; and a working board fixing portion for fixing the working board to a receiving portion of the band saw main body side in a place which the straight line of the laser beam projected from the laser projector and a mark on the working board are aligned.