The present disclosure relates to a semiconductor element 1 including: a gate electrode 2; a source electrode 3; a drain electrode 4; a semiconductor layer 5 that is in contact with the source electrode 3 and the drain electrode 4; and a gate insulating layer 6 that insulates the semiconductor layer 5 from the gate electrode 2, in which the semiconductor layer 5 has a network structure of carbon nanotubes, the semiconductor layer 5 is sealed with a sealing layer 8, and the semiconductor layer 5 has an average thickness of 5 nm or less. The sealing layer 8 preferably contains a compound whose SP value calculated using the Fedors method is 15 (cal/cm3)1/2 or less. Also, the sealing layer preferably has a relative permittivity of 5.0 or less. The sealing layer 8 preferably contains one or more selected from the group consisting of a fluorine-based resin, an acrylic resin, a styrene-based resin, a vinyl-based resin, and an olefin-based resin.