An infrared thermometer such that the measurand includes no error which may be caused due to the transmission of the heat from an object (especially, an external auditory canal), into which a probe is inserted to the probe, to a waveguide and an infrared sensor. In a temperature detecting section where an infrared sensor (40), a waveguide (60) and a temperature sensor (68) are provided in a probe (20), a second thermally conductive tube (34) is so provided between the probe (20) and the waveguide (60) as to be heat insulated from the waveguide (60) and the infrared sensor (40). Thus, the heat from the probe (20) is not transmitted to the waveguide (60) and the infrared sensor (40).