We previously proposed [Jpn. J. Appl. Phys. 34 (1995) L520] a new system for intense-electron-beam transport using an insulator guide which covers the whole beam-transport region. In this paper we present a numerical study of intense-electron-beam transport through an insulator guide whose length is short compared to beam-transport length. Positive ions are extracted in a self-regulated manner from the plasma, generated at the insulator surface, by the electron beam space charge. The ions expand over the transport region, and are extracted from the guide region by the electron beam space charge into the outer region which is not covered by the insulator. Consequently, the beam space charge is neutralized even in the outer region, and the beam propagates effectively in this system.