An object of the present invention is to provide compounds which are useful as protein kinase inhibitors.Disclosed is a 2-aminoquinazoline derivative represented by the following formula (I):wherein R1 represents a lower alkyl group which may be substituted with a halogen atom, or a halogen atom R2 represents a hydrogen atom, a substituted or unsubstituted lower alkyl group, a halogen atom, a hydroxyl group, a substituted or unsubstituted lower alkoxy group, a substituted or unsubstituted amino group, a substituted or unsubstituted acylamino group, a carboxyl group, a lower alkoxycarbonyl group, a carbamoyl group, or a substituted or unsubstituted lower alkylureido group and X, Y and Z each independently represents a hydrogen atom, a substituted or unsubstituted lower alkyl group, a halogen atom, a hydroxyl group, a carboxyl group, a lower alkoxycarbonyl group, a cyano group, a carbamoyl group, a substituted or unsubstituted lower alkoxy group, a substituted or unsubstituted amino group, a substituted or unsubstituted lower alkoxycarbonylamino group, a substituted or unsubstituted lower alkylaminocarbonyl group, a lower alkylsulfonylamino group, a substituted or unsubstituted lower alkylureido group, or a substituted or unsubstituted acylamino group, or X and Y may be combined to form a 5- to 6-membered ring forming a bicyclic fused ring, wherein the 5- to 6-membered ring may optionally have a substituent, provided that when X and Y are not combined to form a fused ring, R2 represents a hydrogen atom and, when X and Y are combined to form a fused ring, a saturated or unsaturated, bicyclic alicyclic or heterocyclic fused ring can be formed.
