A method is provided for producing a benzaldehyde compound represented by the formula (4): wherein Q1 and Q2 represent an alkyl group etc., n represents 1 or 2, and Ar represents a phenyl group etc., including the steps of reacting a compound represented by the formula (3): wherein X1 represents a chlorine atom etc., and Q1, Q2, n and Ar are respectively the same meaning as above, with magnesium metal to obtain a Grignard compound and then reacting the obtained Grignard compound with a formylating agent.