To effectively exhibit the antitumor activities of an amygdalin-containing material in internal use, and further evaluate the effectiveness of the antitumor activities at the time when the amygdalin-containing material is used in the internal use and forecast without carrying out a clinical test.

A seed of a loquat is roasted by far infrared rays, and the roasted seed is fermented by adding a malt. The fermented product is formed into an oil to enhance the antitumor activities thereof. The amygdalin-containing material of which the effects are required to be confirmed is inserted to a system for forming a lipid peroxide by irradiating docosahexaenoic acid with ultraviolet rays, and the antitumor activities are evaluated and predicted so that the larger the increasing proportion of the forming amount of the lipid peroxide based on the concentration- increasing proportion of the amygdalin-contaning material is, the larger the antitumor activities may become at the time of the inner use.