Gas mixing device and substrate processing apparatus

A gas mixing device for mixing plural kinds of gases, comprising:

• a cylindrical portion including an upper surface which is closed;
• a gas outflow passage which is formed in a central portion of a bottom surface of the cylindrical portion, and extends downward;
• a plurality of gas stream guide walls which are disposed to be spaced apart from each other in a circumferential direction along an edge of an opening formed by the gas outflow passage in the bottom surface, and which are installed to be rotationally symmetrical to a center of the cylindrical portion, the plurality of gas stream guide walls protruding toward the upper surface;
• and
• a gas inlet part installed between the plurality of gas stream guide walls and an inner peripheral surface of the cylindrical portion, and into which a gas to be mixed flows,
• wherein, when viewed in one direction of a clockwise direction and a counterclockwise direction in the circumferential direction of the cylindrical portion, if the one direction is defined as a front and the other direction is defined as a rear, the plurality of gas stream guide walls guide the gas introduced between the inner peripheral surface of the cylindrical portion and the plurality of gas stream guide walls to the gas outflow passage along outer peripheral surfaces of the plurality of gas stream guide walls, and the plurality of gas stream guide walls is bent toward the center of the cylindrical portion in a front direction so as to form a swirl flow.