The invention discloses a method and a device for intermediate vulcanization of a natural fiber elastic material, wherein natural fiber yarns are prepared to obtain fiber sheets, and the fiber sheets are superposed and hot-pressed to obtain the natural fiber elastic material. The method is characterized in that an aeration pipe is inserted among the fiber sheets when the fiber sheets are superposed, then the natural fiber elastic material is placed into a vulcanizing tank, the aeration pipe is connected with a hot air pipeline, and hot air is introduced into the aeration pipe to improve the intermediate temperature of the natural fiber elastic material. The vulcanization by the method and the device can improve the elasticity of the fiber elastic material and reduce the possibility of mould development and insect generation of the fiber elastic material. For a fibrous mat obtained through vulcanization, the water content after the vulcanization is lower, and almost no residual odor of the vulcanization exists, thereby improving the mildewproof grade of products, having better elasticity, and being more comfortable.