PURPOSE: To provide a small-sized thermoelectric cooling/heating device in which liquid in a vessel such as a water tank and a beaker, can be simply cooled or heated without filling the element in the liquid in the vessel.

CONSTITUTION: A thermoelectric cooling/heating device comprises the element 1 for cooling or heating at one element surface 1a when a power source voltage is applied and reversely operating at the other element surface 1b, a heat pipe 3 so connected at one end 3a to the element 1a as to be highly thermally conductive, and a heat radiating member 5 so connected to the surface 1b as to be highly thermally conductive.