The common cutworm (Spodoptera litura Fabricius) is a major pest of soybean [Glycine max (L.) Merr.] in southwestern Japan, and other lepidopteran insects damage soybean crops in the United States. Plant resistance to these insects can contribute to integrated pest management. To develop soybean cultivars with insect resistance, resistant germplasms have been identified and used as resistance donor parents. The resistance conferred by their genes has been studied from genetical, morphological, and physiological perspectives. The morphological and physiological approaches have succeeded to some degree, but the main cause of the resistance remains unknown. However, genetic studies have made progress since molecular biological approaches became possible in soybean. Two quantitative trait loci (QTL) for the common cutworm resistance and 23 QTL for other leaf-eating insect resistance have been detected. Actual effects of the major QTL have been confirmed using near-isogenic lines. This progress in genetic studies of the resistance enables the development of elite soybean cultivars with insect resistance, despite the poor agronomic characteristics of resistance donor parents. The present review summarizes the recent progress in resistance to the common cutworm and other insects in soybean.