A process for easily and inexpensively producing an imidazo[1,2-b]pyridazin-3-ylsulfonamide derivative which has a substituent bonded to the 6-position carbon atom and is represented by the formula (II): ##STR00001## (wherein R represents lower alkyl, lower cycloalkyl optionally substituted by lower alkyl, lower alkenyl, or lower alkynyl), the process comprising reacting an imidazo[1,2-b]pyridazine compound represented by the formula (I): ##STR00002## (wherein X represents halogeno or lower alkyl optionally substituted by halogeno; Y represents hydrogen or SO.sub.2N.dbd.CH--NR.sup.1R.sup.2; and Z represents halogeno or OSO.sub.2R.sup.3) with an organometallic compound in the presence of a transition metal catalyst. The derivative is useful as an intermediate for herbicides.