Negative differential resistance with a high peak to valley ratio and low onset voltage is clearly observed in a quantum wire field-effect transistor (QWR-FET) with a channel width of 100 nm, while it is not observed in a QWR-FET with a channel width of 300 nm. The saturation characteristics of Landau plots indicate that the 100 nm wide QWR has one-dimensional characteristics of electron transport, as opposed to the 300 nm wide QWR that has two-dimensional electrons.