PURPOSE: To provide a plasma treating device which can freely control the distribution of plasma treating speed against an objected to be treated, can be improved in uniformity of the treating speed, and can be used for the plasma treatment of semiconductor wafers, etc.

CONSTITUTION: An electron beam 29 is taken out from electron-source plasma, accelerated, and introduced to a reaction chamber 4 and a gas required for plasma-treating an object 15 to be treated set in the chamber 4 is supplied to the chamber 4. Since at least a pair of magnets are opposed to each other across the passage of the electron beam 29 in the chamber 4, the beam 29 is deformed to a sheet-like shape by the magnetic field formed by the magnets and sheet-like plasma is generated by exciting the gas supplied to the chamber 4 with the beam 29. The magnets are positioned so that the treating speed of the object 15 can be made uniform.