112 rot. x-cut LiTaO₃ wafer was used as the substrate of SAW gas sensor. Dual delay line SAW device with IDTs ,which consist of the reference delay line and the sensing delay line was fabricated using photolithigraphy. Each IDTs had 10 forger pairs and finger spacing is 10 microns. One delay line channel is the reference, while the second is the sensing channel with Pb-phthalocyanine film in the propagation path. Pb-phthalocyanine film which is p-type organic semiconductor was evaporated in 10^(-5) torr vacuum using shadow mask selectively. Dual delay line oscillator was constructed by using the rf amplifier and AGC. Frequency of the IDTs had the range of 87-89 MHz oscillation frequency. Oscillation frequency shifts were investigated as a function of the temperature and the concentration of NO₂ gas.