There is provided a semiconductor processing apparatus comprising a processing tube for housing a substrate support member that supports a plurality of substrates stacked at a prescribed pitch in a vertical direction; a gas supply part that extends in a direction in which the substrates are stacked in the processing tube and that has a plurality of gas supply openings; an exhaust part that opens onto the processing tube; a gas rectifying plate that is disposed in a space between a penumbra of the substrates supported on the substrate support member and an inner wall of the processing tube, and that extends from the gas supply part in a circumferential direction of the processing tube and in the direction in which the substrates are stacked; and a gas flow regulating part disposed in a space in the processing tube that is above a top-most gas supply opening and a top-most substrate and in a space in the processing tube that is below a bottom-most substrate and a bottom-most gas supply opening. A thin film formed on the substrate can be made more uniform.