Provided are an efficient method for producing a nitrogen-containing compound or salt thereof to be used in the production of a treatment agent for diseases involving an integrin. Also provided is a production intermediate of the same. A method for producing a novel nitrogen-containing compound or salt thereof, said method comprising: (1) a step for obtaining a compound represented by general formula [10] or salt thereof by an amidation reaction; and (2) a step for deprotecting the compound represented by general formula [10] or salt thereof.