To provide a bar material cutting device capable of cutting a bar material projecting from a wall surface or a floor surface at a part near there and capable of easily cutting a large diameter bar material at a low running cost.

When a fitting member 64 having an annular projection 70 to be engaged with a fitting hole 58 of a chip saw (a disk-like rotary cutting tool) 14 is fastened to a tip of a rotary driving shaft 16, the chip saw 14 itself is slightly deformed into a conical shape. In the condition that a peripheral blade 56 of the chip saw 14 is moved to an opposite side of the rotary driving shaft 16, namely, to a surface 50 side thereof, the bar material 52 is cut. When cutting the bar material 52, the peripheral blade 56 of the chip saw 14 comes closer to the surface 50 side, and the bar material 52 projecting from the surface 50 can be cut at a part near the surface 50.