Thin-film transistors (TFTs) using aligned network of semiconductor-enriched single-wall carbon nanotubes (s-SWCNTs) were fabricated on a SiO2/Si substrate. The aligned thin film was prepared by N2 blow in the drying process using as separated s-SWCNT solution prepared by the agarose gel chromatography. We demonstrated that TFT using a moderately aligned s-SWCNT thin film shows drastically improved transfer characteristics. The TFT simultaneously showed a mobility of 19.6 cm2/(V · s) and an on/off ratio of 1.7 × 105, although the purity of semiconductor used in this work was not higher than 90%. Because the alignment process is very easy and effective, it is expected that moderately aligned s-SWCNT film could be used to practical circuits made of s-SWCNT TFTs.