To provide a sensing element, a vacuum gauge and a vacuum tube which can catch heat diffused 3-dimensionally with a 3-dimensional temperature sensing part, catch the 3-dimensional isothermal contour with the temperature sensing part, to arrange the distance between the heater and the sensing part closer than the distance between the heater and a substrate and to relate to a phenomenon concerning a solid space having heat in the element.

The sensing element comprises a substrate 10 having a penetration hole and a hollow 11, a heater part 13 provided so as to bridge the penetration hole or the hollow 11 having a heating electrode 13-1 having a shape of a bent cantilever and electing into a space, and temperature sensing part 14 and 15 having temperature sensing electrodes 14-1 and 15-1 having a shape of a bent cantilever on the penetration hole or a hollow and erecting into a space. The sensing element measures heat transported from the heater part with the temperature sensing part.