A plasma treatment apparatus and a plasma treatment method having the capability of uniformly treating an object with plasma at a high treatment speed. This apparatus includes a tubular vessel having a laterally elongated cross section, a pair of electrodes arranged such that electric flux lines develop substantially in an axial direction of the tubular vessel when one of an AC voltage and a pulse voltage is applied between the electrodes, a gas supply for supplying a streamer generation gas into the tubular vessel, a power source for applying the voltage between the electrodes to generate plural streamers of the gas in the tubular vessel, and a plasma uniformity mechanism for making the plural streamers uniform in a lateral direction of the laterally elongated cross section of the tubular vessel to provide the plasma from one end of the tubular vessel.