A fibrous structure includes a plurality of fibers consisting substantially of polyimide resin. A ratio of a mass of the plurality of fibers to a mass of the fibrous structure is 70 mass % or more. A thickness of the fibrous structure is 1 mm or more. A basis weight of the fibrous structure is 40 g/m2 or more and 150 g/m2 or less. A length of each of the plurality of fibers may be 1.0 mm or more and 10.0 mm or less. A width of each of the plurality of fibers may be 1 μm or more and 100 μm or less. A thermal conductivity of the fibrous structure measured in accordance with JIS L 1927 may be 0.020 W/m·K or more and 0.040 W/m·K or less.