Interaction cross sections (σ I ) and reaction cross sections(σ R ) are physical quantities which are strongly related to the nuclear size. In our previous study of σ I for Ne isotopes, the deformation features of neutron-rich Ne isotopes in the so-called "island of inversion" region have been successfully observed, and also the formation of the deformed halo structure in 31 Ne has been indicated. In this study, σ I for 19−27 F, up to the vicinity of the island of inversion have been measured at around 240A MeV using BigRIPS at RIBF, RIKEN. Our preliminary results are slightly larger than A 1/3 systematics and some of the data could be explained by nuclear deformation.