To provide a cutting method by a cutter and the cutter lengthening the service life of a band saw machine, and capable of performing efficient cutting by automatically switching wet cutting and dry cutting.

Whether or not to adopt the wet cutting using cutting oil or whether or not to adopt the dry cutting using no cutting oil is preset on various construction materials, and is stored in a database 51. When starting cutting work, a construction material of a work W is inputted from an input means 47. A comparing determining part 53 determines the wet cutting or the dry cutting by comparing the inputted construction material with the construction materials stored in the database 51. When determined to perform the wet cutting, the cutting is performed while supplying the cutting oil by turning on a cutting oil supply device 37. When determined to perform the dry cutting, the cutting is performed by stopping supply of the cutting oil by turning off the cutting oil supply device 37.