The process for manufacturing a platinum temperature-measuring resistance element comprises the step of preparing a thermosensitive part having a portion to be sealed coated with a glaze; the step of placing a pre-sealing element on a tray and inserting the same in a chamber; the step of enclosing a purge gas containing an inert gas and oxygen in the chamber; the step of raising the internal temperature of the chamber to a region in which the platinum is in reduced form at a partial pressure of oxygen in the purge gas as determined from platinum oxide formation free energy; the step of replacing the purge gas with an inert gas wherein oxygen is 1 kPa or below; and the step of under the replaced condition, rapidly heating the furnace interior (interior of the chamber) to a fit melting temperature by means of a lamp heating unit to thereby seal the portion to be sealed of the thermosensitive part.