PURPOSE: To prevent any possible insertion of a sawblade from occurring by retracting a cutting part as far as an optional size at a time when the blade reaches the optional cutting part set to a cutting material, and making it so as to restart the cutting operation from the retracted position, in a band sawing machine.

CONSTITUTION: On the basis of data being inputted from a numerical control system 23, a step feed motion execution plan is calculated and then a cutting down is started. When a step motion is reached to an execution position A, the arrival first time cutting is performed. Next, a housing is lifted up as far as the setting value and the cutting down is restarted, and if the arrival first time cutting is not yet achieved, the step motion is carried out and if it is reached to another execution position B, the arrival first time cutting is performed. If cutting is all over, the housing is lifted up as far as the setting value (e) and the cutting down is performed again. If the cutting of this arrival first time cutting is No, the same operation takes place as to an execution position C of the step motion.