A grommet is provided to securely prevent a wire group from being exposed to water when it is arranged in a water exposure area in a vehicle and while being divided into two or more wire bundles. The grommet includes a conical large diameter portion 12 is provided at one end 11a of a cylindrical main tube 11 made of rubber or elastomer. The other end 11b of the main tube 11 is closed. Two cylindrical branch tubes 13, 14 project from the side surface of the main tube 11 in a direction substantially normal to the longitudinal direction of the main tube 11, and conical large diameter portions 13a, 14a are provided at the leading ends of the branch tubes 13, 14. Furthermore the present invention relates to a method for arranging such a grommet and an use thereof.