PURPOSE: To make linear, high output pseudo-parallelized X-rays securable by opening a part of the side of a small tubular space and making X-ray emitted from there at the time of producing plasma in the small tubular space by creeping discharge along a wall to form the small tubular space, and generating these X-rays.

CONSTITUTION: When a condenser Cd is charged and sufficiently large voltage is impressed on glass 8, a dielectric sheet 9 covering this glass 8 and material 10 are evaporated by creeping discharge of a capillary 2 whereby plasma 5 is produced. At this time, if an electrode beam is irradiated to the plasma 5 from a cathode 6, temperature in the plasma 5 goes up, and plasma density becomes high. And, X-rays 7 in the wavelength area conformed to the material 10 is produced and emitted linearly from a part which is not covered with a dielectric at the side of the capillary 2. In this manner linear, high output pseudo-parallelized X-rays are securable.