The invention discloses a food drying device. A conveying belt (4) is located in a drying furnace body (1). Internal heat exchangers (3) are arranged below the conveying belt (4). An external heat exchanger (2) is arranged on the outer side wall of the drying furnace body (1). An air outlet of the external heat exchanger (2) communicates with an inner cavity of the drying furnace body (1). An air inlet of the external heat exchanger (2) communicates with one end of an air inlet pipe (11). An air inlet fan (10) is arranged at the other end of the air inlet pipe (11). The drying furnace body (1) is provided with an air outlet (6), and the air outlet (6) communicates with one end of an exhaust fan (7). According to the food drying device, it can be guaranteed that the temperature in a drying cavity is high and balanced, and flowing of air in the drying cavity can be accelerated; the heat exchange efficiency is enhanced; foods are heated uniformly; the food drying quality is good; the manufacturing cost is low; operation is simple; the drying effect is good; and energy is saved.