Provided are a novel method of preparing a thienopyrimidine compound having activity of selectively inhibiting tyrosine kinase, particularly, mutant epidermal growth factor receptor tyrosine kinase, and a novel intermediate used for the novel method. According to the method of the present disclosure, a compound of Formula 1 useful as a therapeutic agent for non-small cell lung cancer induced by mutant epidermal growth factor receptor tyrosine kinase can be industrially mass-produced more easily and efficiently than the prior art.
