Means that enables monitoring of an anticancer effect of an anti-CD4 antibody or an anticancer drug targeting an immune checkpoint is disclosed. The method for testing a therapeutic effect of a cancer therapy of the present invention is a method for testing a therapeutic effect of an anticancer drug comprising as an effective ingredient an anti-CD4 antibody or an anticancer drug targeting an immune checkpoint, which method comprises investigation of expression of (1) at least one immune checkpoint receptor, (2) CD8, and (3) at least one cell surface molecule selected from the group consisting of CD44 and CD45RO, on T cells using a sample derived from a patient who received the anticancer drug. Induction of a T cell population which is positive for the immune checkpoint molecule (1) and positive for CD8, and which shows high expression of CD44 and/or high expression of CD45RO, indicates that said anticancer drug is producing a therapeutic effect in said patient.
