To provide a temperature measuring device and a temperature measuring method of a housing that can easily measure a temperature of an outer surface of the housing without removing thermal insulation materials covering a turbine or the like therefrom when the turbine or the like is in operation.

A temperature measuring device 3 for measuring a temperature of an outer surface of a housing 2 comprises: rod-like protrusion members 6 passing through thermal insulation materials 4; fixing members 8 for fixing the thermal insulation materials 4 to the outer surface; and a temperature indicator 10 that is brought into contact with the outer surface and measures the temperature of the outer surface. The protrusion members 6 are disposed such that one ends are connected to the outer surface of the housing 2 and the other ends protrude outwardly from the thermal insulation materials 4. Further, the protrusion members 6 are constituted of nuts 12 fixed to the outer surface of the housing 2 by welding or the like and stud bolts 14 capable of being engaged with the nuts 12. The stud bolts 14 are detachable from the nuts 12. The stud bolts 14 have through holes 16 passing therethrough from one ends to the other ends thereof.