Abstract: The present invention relates to a method for evaluating an efficacy of an anticancer drug or an anticancer drug candidate, comprising the step of treating a mixture of cancer organoids and immune cells with the anticancer drug or the anticancer drug candidate. In addition, it relates to the anticancer drug efficacy evaluation system or anticancer drug screening system comprising cancer organoids and immune cells. The mixture of cancer organoids and immune cells according to the present invention is mixed in a specific ratio, and accordingly can similarly reproduce a tumor microenvironment in which cancer cells exist in the body. Therefore, it can make it possible to accurately predict the efficacy of the drug when administered to a subject.