PURPOSE: To make it possible to maintain vacuum in a vacuum heat treatment furnace and further directly measure the temperature of an area to be measured, by making use of a port in the furnace.

CONSTITUTION: The title temperature measuring apparatus for vacuum heat treatment furnaces, consists of an inserted body 25 that is hermetically inserted into a port 13 in a vacuum heat treatment furnace 1 in such a way that it is freely attachable/detachable; and a sheath type thermocouple 26 that is hermetically inserted into the inserted body 25, and that is brought into contact with the area to be measured in the vacuum heat treatment furnace for the measurement of temperature. This makes it possible to maintain vacuum in a vacuum heat treatment furnace and further directly measure the temperature of an area to be measured using an existing port in the furnace.