To provide an furnace interior situation monitoring method and a furnace interior monitor providing more proper grasping of a furnace interior temperature or the like in a high temperature furnace throughout a long period of time.

A fluid communicating means 11 including a cooling water jacket 11a is provided to contact a furnace body 2 of the high temperature furnace 2, and a heat transfer quantity from a furnace interior to the fluid is measured. The temperature of the furnace interior in a neighborhood of the communicating means 11 is intermittently measured by a temperature measuring means 15 having an opening and closing valve 16, a gas supply means 17, or the like. A temperature evaluation value of the furnace interior is obtained from both measurement data.