Provided are: a compound represented by formula (I)； a retinoid metabolic pathway inhibitor comprising the same； an agent for increasing the ratio of memory T cells； a prophylactic and/or therapeutic agent for cancer or an infectious disease； a cancer immunotherapeutic adjuvant； an immunopotentiator； and a method for preparing a T cell population wherein the ratio of memory T cells is increased, said method comprising using the compound of formula (I).
