According to this configuration, since the heating magnetic body has a structure in which a plurality of flow paths extending rectilinearly from the inlet-side opening toward the exit-side opening of the tubular insulating member are arrayed, pressure loss in the fluid can be reduced. In addition, the heating magnetic body has a shape substantially uniform in the direction in which magnetic lines of force of the electromagnetic induction coil pass (the center axis direction of the tubular insulating member), so that local heat generation is prevented, and the fluid can be heated efficiently.

According to the present invention, the fluid flowing into the annular space through the inflow port is preliminarily heated in the annular space, after which the fluid flows around the communication space, and flows into the tube inside space, to be directly heated by the heating magnetic body. Thus, the high-pressure nitrogen gas is efficiently heated in two stages in the annular space and the tube inside space, before flowing out, so that the fluid heating efficiency is enhanced.

In addition, in the interior of the outer shell member, the annular space outside of the tubular insulating member and the tube inside space inside of the tubular insulating member constitute a single common space together with the communication space. Therefore, even when the fluid flowing in is at a high pressure, there is no difference between the pressures exerted respectively on the outer peripheral surface and the inner peripheral surface of the tubular insulating member, and no stress is generated in the tubular insulating member, so that breakage such as cracking is not generated in the tubular insulating member.