Provided is a technique capable of preventing occurrence of partial discharge. An evaluation apparatus includes a probe disposed on an undersurface of an upper component; a sidewall part disposed on the undersurface of the upper component and enclosing sides of the probe; and a first gas supplying part. The first gas supplying part is capable of supplying a gas to a to-be-measured object that is placed on a stage when the sidewall part comes in proximity to the stage, and to a space enclosed by the stage, the sidewall part, and the upper component when the sidewall part is in contact with the stage.