To provide a semiconductor manufacturing apparatus and a semiconductor manufacturing method, capable of executing film deposition processing, while reducing the distance between a flow-straightening plate and a wafer without opening a reaction chamber and varying a space volume of the upper part of the flow straightening plate, thereby improving the productivity and uniformity of film thickness.

The semiconductor manufacturing apparatus includes: the reaction chamber 11; a gate 16 formed on the wall surface of the reaction chamber 11 and used to carry in and out a wafer w; a gas supply mechanism 12 having an introducing port 12c for introducing a gas to the inside; the flow-straightening plate 12d for discharging the gas in a flow regulated state and a gas supply unit 12a having a predetermined inner volume; a vertical drive mechanism 13; capable of moving the gas supply unit 12a so that the lower surface of the flow straightening plate 12d is situated lower than the position of the gate 16; a gas discharge mechanism 15 for discharging the gas; a support member 17 for supporting the wafer w; and heaters 20a, 20b for heating the wafer w at a predetermined temperature.