Disclosed is a mounting structure of a carrier roller that can decrease vibration occurred in an endless track chain assembly because a location of a carrier roller installed on a lower frame can be controlled. According to the present invention, the mounting structure of the carrier roller is a mounting structure of a carrier roller installed on a lower frame for supporting an upper side of an endless track chain assembly. Further, the mounting structure of the carrier roller includes a mounting part installed on the lower frame, a support part coupled to the mounting part so as to enable its location to be controlled, and a carrier roller coupled to the support part for supporting the endless track chain assembly.