PURPOSE: To provide an ion acceleration electrode plate and its method excellent in durability and anti-corrosion property, with a good cooling performance, without cracking or peeling-off, and capable of being manufactured easily.

CONSTITUTION: A plurality of beam holes 14 are formed on a molybdenum plate along the thickness direction, and a cooling hole 10a serving as cooling water passage is formed in the planar direction of the molybdenum plate orthogonal to the beam holes 14. This plate is composed of grooved molybdenum plate 11 and a molybdenum flat plate 12 being in close contact with the face where a groove 10 is formed by the diffused junction method. This hole 10a is composed of the groove 10 covered with the flat plate 12. At the circumferential part of the hole 10a a ceramic coat 13 is formed by deposition.