Process for producing a 7-bromoquinolone-carboxylic acid derivative of the following formula or its salt ##STR00001## by reacting a 2,4-dibromo-3-hydroxybenzoic acid ester compound of the formula R.sup.7a-x to obtain a 3-alkoxy-2,4-dibromobenzoic acid ester, subjecting the 3-alkoxy-2,4-dibromobenzoic acid ester to elimination reaction of the carboxyl-protecting group to obtain a 3-alkoxy-2,4-dibromobenzoic acid, subjecting the 3-alkoxy-2,4-dibromobenzoic acid to ketoesterification reaction to obtain a 3-alkoxy-2,4-dibromobenyolacetic acid ester, reacting the 3-alkoxy-2,4-dibromobenzoylacetic acid ester with an orthoester or an acetal, then reacting the reaction product with a compound of the formula R.sup.2--NH or its salt to obtain a 2-(3-alkoxy-2,4-dibromobenzoyl)-3-substituted aminoacrylic acid ester and subjecting the 2-(3-alkoxy-2,4-dibromobenzoyl)-3-substituted aminoacrylic acid ester to ring-closing reaction, and products thereof.