To provide methods that can effectively/efficiently increase the amount of vinblastine in Catharanthus roseus.SOLUTION: The present invention provides a method for processing Catharanthus roseus characterized by that while the whole of Catharanthus roseus or at least the part comprising the leaves thereof is irradiated with the light in the wavelength range of 370 nm or more and 400 nm or less in an effective amount to increase the amount of vinblastine in the Catharanthus roseus, the irradiation amount of the light in the wavelength range of 200 nm or more to less than 370 nm to be irradiated on the Catharanthus roseus during the irradiation is less than 20% of the irradiation amount of the light in the wavelength range of 370 nm or more to 400 nm or less.SELECTED DRAWING: Figure 2【課題】ニチニチソウ中のビンブラスチン量を効果的/効率的に増加させることのできる方法を提供すること。【解決手段】本発明は、ニチニチソウの全体又は少なくとも葉部を含む部分に、370nm以上400nm以下の波長域の光を、該ニチニチソウ中のビンブラスチンを増量させるに効果的な量で照射する一方、該照射の間に該ニチニチソウに照射される200nm以上370nm未満の波長域の光の照射量を前記370nm以上400nm以下の波長域の光の照射量の20％未満とすることを特徴とするニチニチソウの処理方法を提供する。【選択図】図２
