To easily deal with a change in the dimensions and the interval of slits and expand the applicable range of a slit cutting work by providing a means for driving a cutter to be rotated, a means for getting the cutter closer to and separating it from a work and a means for feeding the cutter which forms slits at a specified interval.

An operation for feeding a work W by a conveyor is stopped to activate shaft lifting devices 9, 9, and shafts 5, 5 are lowered so that a slit is formed. At the same time, the shafts 5, 5 are again returned to a standby position above after the formation of the slit. After that, the work W is sent over a specified distance by the conveyor 4 and is stopped, and further, the same lifting action is performed by the shaft lifting devices 9, 9 to form the slit in the work W. Thus this sequence of steps is repeated. The length and width of each of the slits are decided by selecting the size of a circular cutter 6 to be used and the depth of the slit into the work W. In addition, the length of the interval between the slits in the longitudinal direction is adjusted by the distance over a single transport by the conveyor 4.