To provide an anti-cancer agent sensitivity determination marker, which marker can determine whether or not the patient has a therapeutic response to the anti-cancer agent, and novel cancer therapeutic means employing the marker.The anti-cancer agent sensitivity determination marker, the anti-cancer agent including oxaliplatin or a salt thereof and fluorouracil or a salt thereof, contains one or more substances selected from among an amino-acid-metabolism-related substance, a nucleic-acid-metabolism-related substance, a substance in the pentose phosphate pathway, a substance in the glycolytic pathway, a substance in the TCA cycle, a polyamine-metabolism-related substance, 7,8-dihydrobiopterin, 6-phosphogluconic acid, butyric acid, triethanolamine, 1-methylnicotinamide, NADH, NAD+, and a substance involved in the metabolism of any of these substances.