Abstract: The present invention provides an endotracheal intubation assist instrument for inserting the bronchofiberscope from the oral or nasal cavity to the trachea easily and then inserting the endotracheal tube into the trachea easily. The side hole 20 is installed near the front edge of the guide tube 10. The guide tube 10 advances naturally from the oral cavity, and the front edge of the guide tube 10 reaches the entrance of the esophagus. The view field is obtained by putting the front edge of the bronchofiberscope 200 onto the base 21. The glottis can be found by the view field of the bronchofiberscope 200 while pulling back the guide tube 10 slowly. The path for the bronchofiberscope 200 from the oral cavity to the esophagus can be secured by the guide tube 10 without influence of the obstacles such as a tongue and an epiglottis, and the operatability can be enhanced. Only the guide tube 10 is removed and the bronchofiberscope 200 remains as the guide line for the endotracheal tube insertion.