To provide a device capable of efficiently/uniformly heating a fluid foodstuff such as jam and various sauces and capable of reducing a cost when heating the fluid foodstuff by carrying an electric current while agitating the foodstuff.

A fluid foodstuff 13 is agitated simultaneously with current- carrying heating by relatively turning agitating electrodes to a vessel while applying voltage between the mutual agitating electrodes by inserting the agitating electrodes 15A and 15B also serving as an agitating member and an electrode by two pieces or more into a cylindrical vessel 11 to house the fluid foodstuff 13. The agiating electrodes are relatively turned to the vessel 11 while applying voltage between the agitating electrodes and a vessel 11 side electrode by inserting one or more agitating electrodes 15A and 15B... into the vessel 11 by forming the electrodes at least on the inner peripheral surface of the cylindrical vessel 11.