A new catalytic combustion-type CO gas sensor was devised by using the precious metal-free CO oxidizing catalyst of 15.9 wt% La_0.87Co_1.13O₃-loaded Ce_0.67Zr_0.18Sn_0.15O_2.0. Since the 15.9 wt% La_0.87Co_1.13O₃-loaded Ce_0.67Zr_0.18Sn_0.15O_2.0 catalyst oxidizes CO completely at 130°C, the sensor showed smooth and reproducible response to CO gas at ca. 130°C. Moreover, the sensor exhibited a linear relationship between response and CO gas concentration, along with short 50% response time of 20–40 s.