There are provided a method of controlling a heating unit of a cooking device, a cooking device and a soybean milk maker. The method of controlling a heating unit (104) of a cooking device comprises: detecting (S110) a conductive property (102) of a mixture (101) of water and food, wherein the conductive property (102) of the mixture indicates a degree of overflow risk of the mixture (101); and sending (S120) a control signal (103) with regard to the heating unit (104) for heating the mixture (101) based on the detected conductive property (102) of the mixture (101) to control the operation of the heating unit (104). With embodiments of the present disclosure, the overflow problem can be solved efficiently at low cost, the structure of the cooking device can be greatly simplified and at the same time the temperature will remain close to the boiling point, which means that the heating process is efficient.