A processing apparatus includes a gas supply passage for supplying a corrosive gas having a halogen, a part of the passage being made of a metal; a stabilization reaction unit which has an energy generator for supplying light energy or heat energy to the corrosive gas that has passed through the metallic part of the gas supply passage and/or has an obstacle configured to apply a collision energy to the corrosive gas that has passed through the metallic part of the gas supply passage, the collision energy being generated from a collision between the obstacle and said corrosive gas. A reaction for stabilizing a compound containing the metal and the halogen contained in the corrosive gas takes place by means of at least one of the light energy, heat energy, and collision energy; and a trapping unit which traps the compound stabilized in the stabilization reaction unit.