To provide a temperature sensor which is inexpensive, excellent in corrosion resistance (especially, sulfidation resistance) and high in followability with respect to temperature change, and also to provide a sulfurization furnace using the same.

In a temperature sensor including a temperature sensing part and a protective tube for protecting the temperature sensing part from atmosphere, a tube whose at least outside surface is made of titanium or titanium alloy is used as the protective tube. As the protective tube, a seamless tube made of titanium or titanium alloy is preferable. Such a temperature sensor can be used for temperature measurement of a sulfurization furnace.