This is the translation of the "DE VERITATE" and the "DE FALSITAS" in the Summa Theologica by St Thomas, Firstly, in these two "Quaestiones", St Thomas gives us the philosophical and ontological definitions about the truth and the falsehood, and also he shows the difference between the "Veritas rei" and the "Veritas intellect", ie, "Truth in things" and "Truth in judgement". At a glance, it seems strange for us to find these "Quaestiones" in his theologia, not in Ontologia. But his Theologia is really his unique Ontologia, therefore he treats about these problems from the ontological point of view. Secondly, we can find out the essence of the philosophy of St Thomas in the later chapters of these "Quaestiones", i. e, the "Intellectualism of St, Thomas". We can describe his definitions of the truth and the falsehcod as follows; "Veritas princlpialiter est in intellectu, secudario in rebus, in online ad intellectum, a quo dependet". "Veritas est adaequatio rei et intellectus" "…… ubi primo est veritas, ibi primo falsitas; ergo falsitas eat in intellectu, et non in rebus nisi in online ad intellectum, ・・・・・・ ergo falsitas secundum quid rei consistit in difformitate ad intellectum per accidens; ergo a quo dependet". Of course, his epistemology is different from the modern ones developed since Renaissance, but we must deeply appreciate his interpretation of the ontological truth and the false-hood, though it clothed the medieval colours.