To provide a thermoelectric needle which allows for a small-diameter structure applicable even to a small animal, in a heating appliance for ablation treatment of tumor.

The thermoelectric needle is constituted by providing a hollow pipe 11 having a closed tip of a preferable external diameter in a range of 1.2-2.0 mm, an electrically insulating tube 2 formed of a heat-resistant insulating material such as polyimide resin and inserted into the pipe, a heating element (heater 3) coated with a heat-resistant insulating material such as polyimide resin and inserted into the tube 2 thus insulating them from each other, and a thermocouple 4, placed in parallel with each other.