Provided are a novel compound having CDK8 and/or CDK19 inhibitory activity, and a production method for Tregs. The treatment of T cells with a CDK8 and/or CDK19 inhibitor induces Foxp3 in the T cells. Foxp3+ T cells can be induced by treating Foxp3−; T cells with the CDK8 and/or CDK19 inhibitor in vitro. Thus, Tregs can be induced.