A discharge device for generating a streamer discharge includes a discharge electrode and a counter electrode. The discharge electrode is in a shape of a wire or rod and is disposed substantially parallel to the counter electrode. Thus, even when a tip of the discharge electrode becomes worn out, a shape of the tip of the discharge electrode remains unchanged and a distance between the discharge electrode and the counter electrode remains unchanged. As a result, even when the tip of the discharge electrode becomes worn out, the streamer discharge stability will not fall.