A cutting tool according to the present invention is coated with one or more Al2O3 layers on at least a part of the surface of a cBN-based sintered material substrate taking part in cutting. The sintered material substrate is made of cBN in an amount of from 20% to 99% by volume and Al2O3 having an average crystalline particle diameter of not more than 1 &mgr;m in an amount of from not less than 1.0% to less than 10% by volume. The Al2O3 layer has a thickness (d) of from 0.5 &mgr;m to 50 &mgr;m. The average crystalline particle diameter (s) of Al2O3 is from 0.01 &mgr;m to 4 &mgr;m if the thickness (d) of the Al2O3 layer is from 0.5 &mgr;m to 25 &mgr;m or from not less than 0.01 &mgr;m to not more than 10 &mgr;m if the thickness (d) of the Al2O3 layer is from more than 25 &mgr;m to 50 &mgr;m.