PURPOSE: To minimize electric charging on the powder and/or particles generated by their contact with the inner wall of a pipe, by modifying the nature of the pipe inner wall through surface activation.

CONSTITUTION: Quality of a pipe 1 is specified according to the substance of transported powder and/or particles 4, and the inner wall of the pipe 1 is irradiated by plasma ions to activate it so as to form a modified surface 2 provided with quality modification treatment effect. This modified surface 2 formed in such a way can minimize the electric charging phenomenon of the powder and/ or particles 4, which is likely to arise when they contact the inner wall of the pipe 1.