To provide an electret whose surface potential is improved and an electrostatic induction conversion device comprising the same, an electret is formed by spin-coating a fluorine-containing polymer composition for coating which contains a fluorine-containing polymer having a ring structure in its main chain, a silane coupling agent, an aprotic fluorine-containing solvent, and a fluorine-containing alcohol as a protic fluorine-containing solvent on a copper substrate and baking it.