A device for continuous heating of fluids, using steam, includes a first tubular circuit, having one inlet and one outlet, in which to fluid or mixture of liquids with gases to be heated is circulated, and a second tubular circuit in which the heating steam is circulated. The first tubular circuit comprises a section that is helically wound around a section of the axial length of a hollow first cylindrical body, closed at both ends. The device further comprises a hollow second hollow cylindrical body in which said first cylindrical body and said helically wound section are coaxially housed. The second cylindrical body is closed at both ends and has radial passageways communicating between the cavity of said first cylindrical body and the cavity of said second cylindrical body. The first cylindrical body, second cylindrical body and radial passageways forming part of said second tubular circuit.