<p>Disclosed is a controlled-potential electrolysis oxygen sensor which can acquire a stable output reliably even if used under a circumstance for frequent dew condensations. The controlled-potential electrolysis oxygen sensor is constituted such that at least a working electrode and a counter electrode are disposed in a casing forming an electrolyte chamber, and such that the quantity of a gas to be detected is limited by a panel cover member having a pin hole formed to extend therethrough and is fed to the working electrode. The controlled-potential electrolysis oxygen sensor is constituted such that a gas-permeable film having a gas-impermeable and a water-repellent outer face is fixed on the outer face of the panel cover member.</p>
