To provide a method of manufacturing an oscillatory power generation element comprising a small-sized and high-output stereoscopic interdigital electrode structure including an electret capable of maintaining a high charge density for a long time.

An oscillatory power generation element is manufactured according to a manufacturing method including: a first step of forming a stereoscopic movable interdigital electrode and a stereoscopic fixed interdigital electrode formed from an Si substrate; a second step of forming an oxide film containing ion on surfaces of the stereoscopic movable interdigital electrode and the stereoscopic fixed interdigital electrode by bringing water vapor containing ion into contact with the electrodes while heating the stereoscopic movable interdigital electrode and the stereoscopic fixed interdigital electrode; and a third step of applying a voltage defining the stereoscopic movable interdigital electrode and the stereoscopic fixed interdigital electrode as a positive side and a negative side, respectively, or as a negative side and a positive side, respectively, between both the electrodes, heating the stereoscopic movable interdigital electrode and the stereoscopic fixed interdigital electrode, and transferring ion contained in the oxide film of the stereoscopic movable interdigital electrode or the stereoscopic fixed interdigital electrode to a surface of the oxide film.