In a carburetor mounting structure, a stud bolt is implanted in a carburetor mounting portion, a screw hole is provided in the carburetor mounting portion, first and second mounting flanges include first bolt holes through which the stud bolt passes, and second bolt holes into which a tap bolt is screwed, and the first bolt hole of the first mounting flange is formed into a notched shape so as to allow the stud bolt to be inserted into the first bolt hole from an outside of the first mounting flange. Thus, it is possible to provide a carburetor mounting structure wherein mounting of a carburetor by a stud bolt is possible even if only a small space exists outward of an outer end of the stud bolt.