[en] We developed a gas-jet transport system coupled to the GAs-filled Recoil Ion Separator GARIS at the RIKEN Linear Accelerator as a novel technique for superheavy element (SHE) chemistry. The isotopes of ²⁶¹Rf (atomic number Z = 104), ²⁶²Db (Z = 105), and ²⁶⁵Sg (Z = 106) useful for chemistry studies were produced in the ²⁴⁸Cm(¹⁸O,5n), ²⁴⁸Cm(¹⁹F,5n), and ²⁴⁸Cm(²²Ne,5n) reactions, respectively, and they were extracted to a chemistry laboratory by the gas-jet method after the separation by GARIS (1-4). The production and decay properties of those isotopes were investigated in detail for future chemistry studies using a rotating wheel apparatus for α and SF spectrometry. Recently, the chemical synthesis and gas-chromatographic analysis of the first organometallic compound of SHEs, Sg(CO)₆, were successfully conducted with preseparated ²⁶⁵Sg. In the conference, preliminary results on the production of Bh (Z = 107) isotopes in the ²⁴⁸Cm(²³Na,xn) reactions will also be presented. (author)