Abstract: An infrared ray clinical thermometer is disclosed. The infrared ray clinical thermometer for detecting infrared rays from an eardrum to measure a body temperature includes the following elements. A main body is provided for being held by hand. A probe part is detachably attached to the main body and has a leading end part for being inserted into an external auditory conduit, the leading end part having an inlet hole for receiving incident infrared rays. An infrared ray sensor is installed within the leading end part of the probe part. The probe part includes the following elements. That is, a hollow speculum is for being inserted into the external auditory conduit. A sensor housing is for accommodating the infrared ray sensor and is adhesively installed within the speculum. An airtight member is provided on a leading end of the sensor housing. The infrared ray sensor is made to approach the eardrum as close as possible, so that the infrared rays from the eardrum can be directly detected.