The interaction cross section ( σ I) was re-measured by a transmission-type measurement for 5 8B 3 at 790 A·MeV on a C target confirming the previously reported value. 8B, although it has a very small proton separation energy 0.137 MeV, shows no remarkable enhancement of the σ I expected from a possible proton halo, as suggested from studies of the quadrupole moment and other recent data such as the reaction cross section at low energies. The root-mean-square (RMS) radius of the nucleon distribution has been deduced using the Glauber model. The relation between the halo tail and the separation energy is discussed on the mirror nuclei 8B and 8Li. It was also found that the previously reported narrow momentum distribution of 7Be from the fragmentation of 8B is well reproduced by the presently determined density distribution.