The invention provides a thermoelectric conversion element having a lot of pn junction pairs per unit area and having a thermoelectric material chip which is hardly broken, and a producing method thereof. In the thermoelectric conversion element of the invention, plural substrates in each of which a film-shaped thermoelectric material is formed in a surface thereof are disposed. As a result, because the number of pn junction pairs per unit area is increased, a high output can be obtained. Because the thermoelectric material is formed into the film shape, reliability degradation caused by a breakage of the thermoelectric material can be prevented, even in the thermoelectric material having many pn junction pairs per unit area, namely, a sectional area is small.