To provide a discharge plasma treatment device having a structure in which a gas flow passage on a gas blowing-out side is hard to break and the flow of a gas on the gas blowing-out side is smooth.

Dielectric boards 4 and 5 extending along the respective planes 2A and 3A of a voltage application electrode 2 and a grounded electrode 3 of counter electrodes 1 are provided, and the tips of the dielectric boards 4 and 5 are projected to the front of a gas blowing-out port 1B to form a gas flow passage, so that the length of the flow passage required for gas rectification is reduced in the gas blowing-out side. Further, the projection length of the dielectric board 4 on the side of the voltage application electrode 2 in the counter electrodes 1 is made shorter than the projection length of the dielectric board 5 on the side of the grounded electrode 3, so that a smooth gas flow is formed.