The invention discloses an inner chamber type injection device (1). The injection device comprises an injection hood (2) and an injection pipe (3) connected to the injection hood (2). The injection hood (2) is internally provided with an injection cavity chamber (201), an injection branch pipe (302) is internally communicated with the injection cavity chamber (201), and an injection hole (202) isformed in the inner wall of the injection hood (2). According to the inner chamber type injection device, the injection structure form is changed, a gas flow passage is changed from an injection pipeinto a cavity of the inner wall of the injection hood, a gas ejection outlet is changed from an injection hole into an opening of the inner wall of the injection hood, gas injected into the hood through the cavity of the inner wall and the opening of the inner wall of the injection hood is fully mixed with the air in the hood, and the pipe discharging structure in the prior art is eliminated, so that the problems of the prior art are effectively solved, the mixing uniformity of the gas and air in the injection hood is improved, and the service life of the injection device is prolonged. Compared with the prior art, the inner chamber type injection device is more reliable, safer and more stable and has great potential for development.