To obtain a heat resistant probe which is not broken easily in a heating environment exposed to radiation heat and the surface of front lens can be protected without sacrifice of measurement accuracy by providing a mechanism for protecting the laser beam collecting front lens in the probe of a laser current meter against radiation heat.

A filter 2 is screwed into a tubular stainless steel housing 1 on the forward end side thereof. The filter 2 comprises two sheets of superposed filter 2, 2. The outside filter 2 has front face coated with an infrared reflection film 2a which reflects infrared rays causing radiation heat effectively. The infrared reflection film 2a is formed by combining one or more than one kind of Al-Ge-SiO, Cu-Ge-SiO, AuGe-SiO, or the like, appropriately. An infrared ray absorbing film 2b is applied between the filters 2, 2 in order to absorb transmitted infrared rays thus suppressing intrusion of heat rays into the probe, especially to the front lens side.