A band saw machine with a disk brake device is provided. A lower gravity wheel is provided with a disk which is turned synchronously. The circumferential edge of the disk is provided with a brake seat. A brake wire provided at the bottom of the band saw machine is connected with a brake lever which can be pivoted. The upper end of the brake lever is in contact with a micro switch seat. Thereby, when the brake lever is pressed, the upper end of the brake lever is away from the micro switch seat, such that the band saw machine is cut off the power supply to stop running. The brake wire links the crank of the brake seat. The brake seat brings a brake action to the disk, such that the lower gravity wheel stops running so as to stop the operation of the saw band of the band saw machine. The present invention provides practical effects of emergent stopping and safety.