Abstract: The present invention relates to a novel combination of (1) a substance that suppresses or inhibits the function of extracellular TCTP (translationally controlled tumor protein), especially released from tumor cells, and (2) a cancer immunotherapeutic agent for the treatment of cancer. Preferably, such a cancer immunotherapeutic agent is an immune checkpoint inhibitor. The substance that suppresses or inhibits the function of extracellular TCTP functions as an activator or enhancer of anti-tumor immune cells including T cells and natural killer (NK) cells and/or an antagonist of immunosuppressive cells, such as myeloid-derived suppressor cells (MDSCs), in the tumor immune microenvironment (TIME). The combination according to the present invention is useful for treating or preventing cancer. The combination according to the present invention is also useful for alleviating, reverting, or preventing immune suppression in the tumor immune microenvironment.