We developed a chemical gas sensor using SWCNT(single-walled carbon nanotubes) with nanoscale electrode-interval. To fabricate electrode pattern, we designed at first a continuous electrode pattern without any intervals. Then, the nanoscale interval was formed by a nanoscale trench using a sacrificial oxide layer located at the center of electrode. By this technique we obtained an electrode pattern with 100 nm interval. Though, the nanoscale interval can be realized by various nanolithography techniques including nanoimprint, nano-MEMS technology is not yet standardized and still requires great expense for even a stamp fabrication. Our method consisted of well developed processes for microscale semiconductor fabrication including trench formation, polysilicon deposition, and thermal oxidation. We expect that our method will induce high reproducibility and is closer to the commercilization of nanotube based gas sensor with higher sensitivity.