Although compounds for treating or ameliorating malignant diseases have been proposed, patients had to endure a large burden since many of such compounds could not be orally ingested. Mangiferin has an effect of ameliorating malignant diseases through oral ingestion. However, such effect is minor and realistically it was not easy to ingest mangiferin. Further, in order to develop more effective pharmaceutical agents and the like for treating malignant diseases, it has been considered constantly necessary to obtain new or improved forms of an existing medical agent for inhibiting kinases such as NIK. A compound represented by formula (11) has an effect of ameliorating malignant diseases through oral ingestion, and can exhibit said effect with an amount less than that for mangiferin.