A recognition method of a kerf includes a bonding step of bonding a workpiece to a dicing tape greater in size than the workpiece, a pre-machining imaging step of imaging an optimal region of the dicing tape where the workpiece is not bonded, a kerf forming step of forming a kerf in the optimal region by a cutting machine, a post-machining imaging step of imaging the optimal region with the kerf formed therein, and a recognition step of comparing intensities of light received at each two corresponding pixels in respective images of the optimal region as acquired by the pre-machining imaging step and the post-machining imaging step, subtracting the each two pixels where intensities of received light are the same, and recognizing as the kerf a region formed by the remaining pixels.