A co-crystal consisting of a diamide-based insecticidal active component and a neonicotinoid-based insecticidal active component may exhibit excellent insecticidal effects for a long-term period while minimizing the occurrence of chemical-induced damage in useful plants. The co-crystal is obtained using a method which includes heating and stirring a suspension obtained by dispersing the diamide-based insecticidal active component and the neonicotinoid-based insecticidal active component in a solvent such as water.提供一種共結晶,其係抑制對有用植物之藥害發生並且長期呈現優異之殺蟲效果者,且係由二醯胺系殺蟲活性成分與新菸鹼類系殺蟲活性成分構成。該共結晶可藉由包括使二醯胺系殺蟲活性成分及新菸鹼類系殺蟲活性成分懸浮於水等溶劑,然後將獲得之懸浮液加熱、攪拌之方法而獲得。