Abstract: An immersion-type temperature measuring apparatus using a thermocouple for measuring temperature of a melt, which comprises: a replaceable cartridge-type temperature sensor (11) for detecting a thermoelectromotive force corresponding to a temperature of a melt, the temperature sensor (11) comprising a thermocouple (13), a protecting tube (12) for protecting the thermocouple (13) from the melt, and a connector (16); a holder for releasably supporting the temperature sensor (11); a measuring instrument (28) for processing the thermoelectromotive force to determine the temperature of the melt; and an extension lead wire (25) for connecting the temperature sensor (11) with the measuring instrument (28). At least part of the above-mentioned protecting tube (12) is formed of a molybdenum-zirconia refractory consisting essentially of from 20 to 95 wt. % molybdenum and from 5 to 80 wt. % zirconia.