To improve conversion efficiency of a mechanical electric energy conversion device using Electret.

In a mechanical electric energy conversion device 10, as an example, an electret holding body 11, to which an electret film 12 is applied, is faced to a working electrodes 13 and 14, and a potential of opposite sign to the electret surface charge is induced thereto. Accordingly, if a holding body 11 moves right and left, a current is caused to flow at a load 15. Although a metal body is stuck on the electret film 12 in an electrostatic charge step of the electret film 12 in a conventional way and a surface charge density is made high, the electret film 12 is supported as a self-supported film or supported on an insulating supporter 11 in a stage where it is used for mechanical electric energy conversion. Then, the amount of effective charge induced on the surface of the working electrodes 13 and 14 is raised.