Abstract: Disclosed is a CNT nanodevice using small-diameter CNT having a monolayer, two-layer or other structure produced by virtue of strong CNT fastening treatment under high vacuum of an environment having a very low residual hydrocarbon content. Also disclosed are a CNT supporting body such as a CNT holding body necessary for the production process of the CNT nanodevice, and a process for producing the CNT supporting body. A supporting portion (18a) is provided on a supporting body (18). A base end portion (15a) in CNT (15) is transferred to the supporting portion (18a), and electron beams (17) or ion beams are applied toward the base end portion (15a) in CNT (15). A carbon material layer (19) covering the base end portion (15a) and the supporting portion (18a) is converted to an amorphous carbon layer and a graphite layer by the application of the beams. CNT (15) is fixed to the supporting body (18) by the graphite layer to produce the CNT supporting body.