a reactive ionized cluster beam deposition method according to this invention is embodied by utilizing two vacuum subregions partitioned by a partition wall formed with an opening . a closed heating crucible and an ionization accelerating unit are disposed in one vacuum subregion partitioned by the partition wall . a substrate is also disposed in the other vacuum subregion , and at the same time a reactive gas is introduced thereinto . degrees of vacuums in the two vacuum subregions partitioned by the partition wall are equal to or different from each other . particularly , a gas concentration in the latter vacuum subregion is enhanced . then , the ionized cluster beams formed in the former vacuum subregion are introduced into the latter vacuum subregion via the opening of the partition wall and react to the reactive gas within the latter vacuum subregion . the ionized cluster beams reacting to the reactive gas impinge on the substrate , thereby forming the deposited film on the substrate surface .