A manufacturing method of a top plate hermetically attached to an upper opening of a tubular shaped container body for forming a processing container of a plasma processing apparatus is provided. The manufacturing method includes the steps of; preparing a top plate body comprised of a dielectric body for transmitting an electromagnetic wave, and having a gas ejection hole for ejecting a gas into the processing container; forming a discharge prevention member having a discharge prevention member body comprised of a dielectric body having a permeability, and a dense member comprised of a dielectric body without a permeability covering at least a side face of the discharge prevention member body; and attaching the discharge prevention member in the gas ejection hole of the top plate body.