Abstract: The deep fryer comprises an oil tank, an immersed heater (3) controlled by a thermostat (2) which disconnects the heater when the oil reaches a given temperature. The thermostat comprises an auxiliary switch (a) which controls a signal light (a-1) or some other signalling means operating at a temperature 5.degree. to 10.degree. C. below the operating temperature of the main switch (b) which controls the heater. One thus anticipates the time when the required temperature is reached. By immersing the product to be fried at that moment, one eliminates the inertia effect of the thermostat, prevents the disconnecting of the heater, and reduces the drop in temperature. The duration of the cooking cycle is reduced.