Provided are a method for producing a sulfonyl amidine compound, which has an excellent gonadotropin releasing hormone receptor antagonism and is useful as a therapeutic agent for gonadotropin-dependent diseases (for example, prostate cancer, breast cancer, endometriosis, uterine fibroid, prostatic hyperplasia, or the like) or a salt thereof, and a synthesis intermediate useful in the production method. The production method of the present invention controls formation of a by-product which is hardly removed unless column purification is conducted and racemization of a target compound, thereby obtaining the target compound with a high purity, and therefore, the production method is suitable for industrial production.