PURPOSE: To improve an yield in the manufacturing process by providing a needle having steps or a group of minute unevenness on the surface.

CONSTITUTION: When tungsten is used for making a needle having the tip radius of several μm, serving as an electric field emittive liquid metal ion source, etching is performed for a short time in the process of etching in the sodium hydroxide solution followed by stopping it for raising the position of the needle a little while resuming etching for a short time. By repeating said operation, a large number of steps 5 can be obtained. In this way, a needle 1 having steps 5 is used for enabling a large number of liquid metal partitculates 6 to stick to the recessed parts for improving an yield in the manufacturing process, thus to form uniform the wet of the liquid metal on the tip of the needle 1. Further, a group of minute unevenness may be formed in place of the steps 5.