The present invention provides an antitumor agent or postoperative adjuvant chemotherapeutic agent for a hepatocellular carcinoma patient who has been treated by transarterial embolization. An antitumor agent or postoperative adjuvant chemotherapeutic agent comprising TSU-68 or a salt thereof, which can be administered to a hepatocellular carcinoma patient within 2 weeks after transarterial embolization, is provided.