The invention provides a non-invasive detecting apparatus for fruits or vegetables, and ranking method thereof. The non-invasive detecting apparatus includes: a heater, configured to operably heat the fruits or the vegetables, by leaning the heater on a surface of the fruits or the vegetables; a temperature sensor, configured to operably sense a temperature variation level of the fruits or the vegetables, after heating the fruits or the vegetables by the heater; a processor, electrically coupled to the heater and the temperature sensor; a power supply, electrically coupled to the processor for supplying a power to the processor; and a user control unit, electrically coupled to the processor, for turning on, turning off, or setting the heater. According to the aforementioned temperature variation level, a ranking method for the non-invasive detecting apparatus for fruits or vegetables includes: a lowest temperature variation level corresponds to a highest sweetness, and a highest temperature variation level co
