To provide bar material cutting device and disc type rotary cutting tool for preventing relative rotation of a rotary drive shaft and the disc type rotary cutting tool by a constitution having excellent durability.

A chip saw 14 to be the disc type rotary cutting tool is provided with an engagement groove 64 having a torque transmission surface 66 going toward the outer peripheral side continuously from a circular inner peripheral surface 62 of a mounting hole 60. Accordingly, sectional area of a shearing direction around a shaft center of the rotary drive shaft 16 in an engagement projection 72 engaged to the engagement groove 64 provided at an end part of the rotary drive shaft 16 is increased as much as possible, while suitably suppressing an outer diameter D of an annular abutting surface 70 allowed to abut on the chip saw 14 in the rotary drive shaft 16. Namely, the bar material cutting device 10 and the chip saw 14 for preventing relative rotation of the rotary drive shaft 16 and the chip saw 14 by the constitution having excellent durability are provided.