A cooking method using an automatic pressure double boiler is provided. The cooking method can prevent steam containing the medicinal or nutritive components in the medicine or health food from leaking out of the cooking pot, and thus keep the medicinal or nutritive effect of the medicine or health food, compared with conventional cooking methods, such as baking with fire, boiling with water, frying with oil, steaming, etc. The cooking method does not allow the boiled water or steam to enter the inner cooking pot, thereby acquiring pure medicinal or nutritive components from the medicine or health food. Since the cooking method heats the medicine or food with the energy of the steam from the boiled water, not direct or conducted heat energy from an electric heater, it cannot burn the medicine or food although it heats it to extract the pure medicinal or nutritive components and condenses them.