A sampling nozzle 21, an ion supply tube 31 leading to an analysis apparatus 50 and a barrier discharge tube 11 are connected to first, second and third ends, respectively, of a T-shaped tube 41 having three connecting ports, and the central portion of the T-shaped tube is an ionization chamber SP. The ionization chamber SP is a closed space, and ions generated therein are introduced to the analysis apparatus 50 through the ion supply tube 31. As a result, almost all of the ions are introduced into the interior of the analysis apparatus.