An injection molding machine with a hot mixing device comprises a base, a controller, a crate and an injection gun. The injection gun is provided with a feeding inlet. A hot mixing tank which communicates with the feeding inlet is arranged on the feeding inlet. A stirring structure is arranged in the hot mixing tank, and a driving device used for driving the stirring mechanism to rotate is arranged outside the hot mixing tank. A second injection gun used for feeding materials to the hot mixing tank is connected to the upper portion of the hot mixing tank and provided with a second feeding inlet. A feeding hopper is arranged on the second feeding inlet. The defects in the prior art are overcome, the hot mixing tank and the second injection gun are connected to an existing injection gun in sequence, raw materials enters the second injection fun at first, subjected to hot melting through the second injection gun, conveyed into the hot mixing tank, stirred and mixed in the hot mixing tank, then conveyed into the injection gun through spiral blades on the lower portion, injected into a mold through the injection gun at last and stirred and mixed after hot melting, mixing is uniform, the effect is good, and the application range is wide.