PURPOSE: To obtain a from which stable and long-life ion beams of elements with high melting points such as B, Si, P, As, etc. can be extracted by using an alloy consisting of two or more kinds of transition metal element and two or more kinds of element selected from a group composed of B, Si, P, C, Al, and As.

CONSTITUTION: Suppose that M inplies two or more kinds of element selected from a group of transition metal element and X inplies two or more kinds of element selected from a group consisting of B, Si, P, Al, and As, an alloy that has the composition expressed by a general equation MaXb and satisfies the conditions 31≤b≤60 and a+b=100 is used as the ion species material. If such a binary alloy is used, the life span of an ion source can be extended up to 100hr. In addition, an alloy material consisting of three or more elements in which X implies two or more elements selected from a group of B, Si, P, C, Al, and As and the rest consists of transition metal elements can more suppress the reaction against an emitter chip as compared with a two-element alloy material, its wetting pooperty can be improved, and the higher life span of the ion source can be achieved.