In recent years, research of metal oxide semiconductor-based sensors has focused on morphology modification of thin film structures. One of the promising materials that is being developed is SnO₂. In this research, nanostructured SnO₂ thin film was grown using the ultrasonic spray pyrolysis and chemical bath deposition methods with and without external magnet assistance (0.1 T). As precursor solution of the ultrasonic spray pyrolysis process, the SnCl₂·2H₂O is dissolved in distilled water, with pH varied by adding 37% HCl solution. The precursor solution for the chemical bath deposition process was SnCl₂·2H₂O, which is dissolved in urea solution with pH customized by adding the NaOH solution. All resulting nanostructured SnO₂ thin film samples were characterized by using X-ray diffraction and scanning electron microscopy techniques. The resulting morphologies of SnO₂, prepared by chemical bath deposition, using magnetic field, HMTA framework-assisted chemical bath deposition, and ultrasonic spray pyrolysis are spherical, cubic, and spherical, respectively. The sensor response pattern of nanostructured SnO₂ thin films, prepared by all tested methods, to 30 ppm CO, is similar in that the response increases with the increase of working temperature. The SnO₂ thin film prepared by ultrasonic spray pyrolysis method shows the greatest sensitivity value of 95.12%, with a response time of 216 seconds and a recovery time of 558 seconds, at working temperature of 300 degrees Celsius.