To obtain a spiral inductor in which signal loss is reduced by providing an insulating substrate, a wiring section having stripe conductors wound planarly and spirally and arranged in parallel with the substrate, a part touching the substrate, and a hollow wiring having a specified gap with respect to the substrate.

The spiral inductor comprises an Si oxide film 104 of 2000 thick formed on an Si substrate 103, and a lower layer wiring 105 is formed by laminating a gold film of 0.5 μm thick, a platinum film of 0.1 μm thick, and a Ti film of 0.05 μm thick. An Si nitride film 106 of 2000 thick is formed on the lower layer wiring 105 and an upper layer wiring 107 is formed by laminating a gold film of 10 μm thick, and a Ti film of 0.05 μm thick thereon. The upper layer wiring 107 comprises a hollow section 102 and a part 101 touching the substrate 108 wherein the gap between the upper layer wiring 107 and the surface (Si nitride 106) of the substrate 108 is set at 2 μm and the area of the hollow section 102 is set larger than that of the contact part 101.