Synopsis Ion beam guiding effect of macroscopic-size single insulator capillaries was studied with keV-energy Ar8+.Straight and curved capillaries made of a few glass materials and Teflon were used as samples.Each capillary was about 50 mm in length, 0.8-1.1 mm and 1.1-2.0 mm in inner and outer diameters, respectively.A certain transmission was observed even for curved capillaries of bending angles more than 10 degrees, while transmission through straight ones vanished when the tilt was more than 6 degrees.