The present invention provides a thermoelectric conversion material represented by the following chemical formula Mg 3+m A a B b D 2-e E e . The element A represents at least one selected from the group consisting of Ca, Sr, Ba and Yb. The element B represents at least one selected from the group consisting of Mn and Zn. The value of m is not less than -0.39 and not more than 0.42. The value of a is not less than 0 and not more than 0.12. The value of b is not less than 0 and not more than 0.48. The element D represents at least one selected from the group consisting of Sb and Bi. The element E represents at least one selected from the group consisting of Se and Te. The value of e is not less than 0.001 and not more than 0.06. The thermoelectric conversion material has a La 2 O 3 crystalline structure. The thermoelectric conversion material is of n-type. The present invention provides a novel thermoelectric conversion material.