One of the new applications of focused Ga ion beam (Ga FIB) techniques to fabricate micro fluid channels on plate glass was demonstrated. After discussing features of the FIB etched patterns, narrow channel or Y-shaped channels were fabricated by FIB etching on a patterned plate glass which was prepared by photo-lithography and wet etching processes. Micro fluid devices were then constructed using polydimethylsiloxane (PDMS) sheet and silicone rubber tubes and the water (or ink) flow in the devices was observed under a microscope using a syringe pump. Although no discussion based on fluid mechanics has done at present, the present results indicate a possibility of applying FIB techniques to fabricate micro fluid devices which can be used in bio- and/or chemical-related fields.