<p>This thin-film forming device includes: a deposition vessel in which a reduced-pressure deposition space, to which a raw material gas and a reactant gas are alternately supplied on different timings, is formed in order to form a thin film on the substrate; and a gas supply unit configured to supply the raw material gas and the reactant gas to the deposition vessel. The gas supply unit is provided with at least one partition that bends a gas passage from an inlet port of each of the raw material gas and the reactant gas toward the deposition space.</p>
