The radiation detector manufacturing method and film forming apparatus

A layer-forming apparatus coats a solution containing a layer component and a flammable solvent on a surface of a base material, and forms a layer on the surface of the base material. In the layer-forming apparatus, a coating chamber in which the solution is coated on the surface of the base material is closed substantially hermetically, and a clean air is supplied from a clean-air supplier to the coating chamber. Then, ions that are produced by a corona discharger are sprayed to the surface of the base material in a state that a vapor concentration of the solvent in the coating chamber is below a burning lower limit, and dusts are removed from the base material. Then, the solution is coated on the surface of the base material from which the dusts are removed.