The measurement temperature characteristics in a semi-opened furnace used for performance evaluation of medium/low temperature ceramic fuel cells were experimentally examined. Temperature measurement positions were classified into two cases with the attached condition (A thermocouple is in contact with fuel cell surface) and the floated condition (A thermocouple is apart from the fuel cell surface). Compared to the floated condition, the attached condition exhibits the characteristics of higher measurement temperature and better temperature stability. When the measurement temperature of the attached and floated conditions based on calibrated temperatures were controlled to 250°C, the peak power density of ceramic fuel cells with yttrium-doped barium zirconate thin-film electrolyte was measured at approximately 50% smaller for the attached condition comparison with the floated condition. Comparison of the ohmic area specific resistance for ceramic fuel cells with yttria-stabilized zirconate substrate electrolyte showed that, for the performance evaluation reliability, the attached condition is more appropriate than the floated condition.