A camptothecin-containing pharmaceutical composition which contains: (a) camptothecin or a derivative thereof, and (b) one or more compounds selected from among ascorbic acid or a salt thereof, sodium hydrogen sulfite, sodium sulfite, potassium pyrosulfite, sodium erythorbate, sodium thioglycolate, sodium pyrosulfite, and α-thioglycerin. The pharmaceutical composition is useful in that, after storage for a long period of time or under light-irradiation conditions, camptothecin or a derivative thereof contained therein undergoes minimum degradation.