To reduce the weight of an exhaust pipe by using a material with low specific gravity such as titanium for the exhaust pipe, and to prevent a component to be screwed to the exhaust pipe from loosening.

When an exhaust gas sensor 11 is mounted on the exhaust pipe where an exhaust gas flows from an engine, an intermediate member 24 is interposed between the exhaust gas sensor 11 and a boss 16 attached to an exhaust collection pipe 9, the intermediate member 24 is fastened to the boss 16 by bolts 29, and a sensor section 14 at a tip end of the exhaust gas sensor 11 is inserted into the exhaust pipe 9 by screwing the exhaust gas sensor 11 to a screw hole 26 formed on the intermediate member 24. The screw hole 26 formed on the intermediate member 24 is exposed to hot gas of the exhaust collection pipe 9, while a female screw in the screw hole 26 is hardly softened by using a stainless steel with large high-temperature strength for the intermediate member 24, and torque down can be prevented.