A thermoelectric conversion element includes a pair of electrodes and a pyroelectric material, which is a ferroelectric layer, sandwiched between the pair of electrodes. The pyroelectric material includes at least Bi (bismuth), La (lanthanum), and Fe (iron). The molar fraction of La in a Bi/La site in the crystal structure of the pyroelectric material is 0.15 or more and 0.20 or less. Such a thermoelectric conversion element, and a light detection device and electronic apparatus which include the thermoelectric conversion element have a good pyroelectric function without including Pb (lead).