A method for manufacturing a crystalline silicon-based photoelectric conversion device, wherein the crystalline silicon-based photoelectric conversion device comprises: an intrinsic silicon-based layer of a first conductivity type layer-side and a silicon-based layer of a first conductivity type, in this order on one surface of a single-crystal silicon substrate of the first conductivity type; and an intrinsic silicon-based layer of an opposite conductivity type layer-side and a silicon-based layer of an opposite conductivity type, in this order on another surface of the single-crystal silicon substrate of the first conductivity type, the method comprising: at least one of a step of forming the intrinsic silicon-based layer of the first conductivity type layer-side and a step of forming the intrinsic silicon-based layer of the opposite conductivity type layer-side, the at least one step including substeps in the following order: a step of forming a first intrinsic silicon-based thin-film layer having a thickness of 1 nm to 10 nm on the single-crystal silicon substrate of the first conductivity type; a step of plasma-treating the single-crystal silicon substrate of the first conductivity type, on which the first intrinsic silicon-based thin-film layer is formed thereon, in an atmosphere of a gas containing hydrogen as a main component; and a step of forming a second intrinsic silicon-based thin-film layer on the first intrinsic silicon-based thin-film layer, wherein the content of a raw material gas in the step of plasma-treating the single-crystal silicon substrate is 1/100 or less of the content of hydrogen on a volume basis, the raw material gas being gas used for forming the first intrinsic silicon-based thin-film layer, wherein a sum of thicknesses of the first intrinsic silicon-based thin-film layer and the second intrinsic silicon-based thin-film layer is 16 nm or less, and wherein the intrinsic silicon-based layers of first and opposite conductivity type layer-sides are non-doped silicon-based layers. at least one of a step of forming the intrinsic silicon-based layer of the first conductivity type layer-side and a step of forming the intrinsic silicon-based layer of the opposite conductivity type layer-side, the at least one step including substeps in the following order: a step of forming a first intrinsic silicon-based thin-film layer having a thickness of 1 nm to 10 nm on the single-crystal silicon substrate of the first conductivity type; a step of plasma-treating the single-crystal silicon substrate of the first conductivity type, on which the first intrinsic silicon-based thin-film layer is formed thereon, in an atmosphere of a gas containing hydrogen as a main component; and a step of forming a second intrinsic silicon-based thin-film layer on the first intrinsic silicon-based thin-film layer, wherein the content of a raw material gas in the step of plasma-treating the single-crystal silicon substrate is 1/100 or less of the content of hydrogen on a volume basis, the raw material gas being gas used for forming the first intrinsic silicon-based thin-film layer, wherein a sum of thicknesses of the first intrinsic silicon-based thin-film layer and the second intrinsic silicon-based thin-film layer is 16 nm or less, and wherein the intrinsic silicon-based layers of first and opposite conductivity type layer-sides are non-doped silicon-based layers. a step of forming a first intrinsic silicon-based thin-film layer having a thickness of 1 nm to 10 nm on the single-crystal silicon substrate of the first conductivity type; a step of plasma-treating the single-crystal silicon substrate of the first conductivity type, on which the first intrinsic silicon-based thin-film layer is formed thereon, in an atmosphere of a gas containing hydrogen as a main component; and a step of forming a second intrinsic silicon-based thin-film layer on the first intrinsic silicon-based thin-film layer, wherein the content of a raw material gas in the step of plasma-treating the single-crystal silicon substrate is 1/100 or less of the content of hydrogen on a volume basis, the raw material gas being gas used for forming the first intrinsic silicon-based thin-film layer, wherein a sum of thicknesses of the first intrinsic silicon-based thin-film layer and the second intrinsic silicon-based thin-film layer is 16 nm or less, and wherein the intrinsic silicon-based layers of first and opposite conductivity type layer-sides are non-doped silicon-based layers.