An injection nozzle (30, 30A-30D) of a wax mold injection molding machine, comprising: an outer cylinder having an inner wall; an inner cylinder having an inner wall and an outer wall, and movable in a front-rear direction; a wax flow channel defined by the inner wall of the inner cylinder, and communicating with an inner cylinder opening at a front end of the inner cylinder; an exhaust flow channel defined between the inner wall of the outer cylinder and the outer wall of the inner cylinder, and communicating with an outer cylinder opening at a front end of the outer cylinder; a wax valve for opening and closing the wax flow channel, and an exhaust valve for opening and closing the exhaust flow channel, wherein: the outer cylinder includes a small-inside-diameter part to which the outer cylinder opening is formed, and an inner surface tapered part whose inside diameter increases from the small-inside-diameter part to rearward, and the inner cylinder includes a small-outside-diameter part to which the inner cylinder opening is formed, and an outer surface tapered part whose outside diameter increases from the small-outside-diameter part to rearward, characterized in that: the exhaust valve includes a seal member attached to the outer surface tapered part, or a portion rearward of the outer surface tapered part and having a larger diameter than the small-outside-diameter part. an outer cylinder having an inner wall; an inner cylinder having an inner wall and an outer wall, and movable in a front-rear direction; a wax flow channel defined by the inner wall of the inner cylinder, and communicating with an inner cylinder opening at a front end of the inner cylinder; an exhaust flow channel defined between the inner wall of the outer cylinder and the outer wall of the inner cylinder, and communicating with an outer cylinder opening at a front end of the outer cylinder; a wax valve for opening and closing the wax flow channel, and an exhaust valve for opening and closing the exhaust flow channel, wherein: the outer cylinder includes a small-inside-diameter part to which the outer cylinder opening is formed, and an inner surface tapered part whose inside diameter increases from the small-inside-diameter part to rearward, and the inner cylinder includes a small-outside-diameter part to which the inner cylinder opening is formed, and an outer surface tapered part whose outside diameter increases from the small-outside-diameter part to rearward, characterized in that: the exhaust valve includes a seal member attached to the outer surface tapered part, or a portion rearward of the outer surface tapered part and having a larger diameter than the small-outside-diameter part. the outer cylinder includes a small-inside-diameter part to which the outer cylinder opening is formed, and an inner surface tapered part whose inside diameter increases from the small-inside-diameter part to rearward, and the inner cylinder includes a small-outside-diameter part to which the inner cylinder opening is formed, and an outer surface tapered part whose outside diameter increases from the small-outside-diameter part to rearward, characterized in that: the exhaust valve includes a seal member attached to the outer surface tapered part, or a portion rearward of the outer surface tapered part and having a larger diameter than the small-outside-diameter part.