The present invention provides a fused heterocyclic compound having a tyrosine kinase inhibitory action, which is represented by the formula: wherein ring A is an optionally substituted benzene ring； ring B is an optionally substituted benzoisothiazole ring； R 1 is a hydrogen atom, a halogen atom, or an optionally substituted group bonded via a carbon atom, a nitrogen atom or an oxygen atom； R 2 is a hydrogen atom, or an optionally substituted group bonded via a carbon atom or a sulfur atom； R 3 is a hydrogen atom or an optionally substituted aliphatic hydrocarbon group； or R 1 and R 2 , or R 2 and R 3 are optionally bonded to each other to form an optionally substituted ring structure； or R 3 is optionally bonded to the carbon atom on ring A to form an optionally substituted ring structure； or a salt thereof.
