Endoscopic endonasal skull base surgery has become popular due to its minimally invasive nature to the patient and the development of various medical devices. The reason why it is considered less invasive is that it is possible to reach the anterior skull base lesion using the corridor of the nasal cavity and paranasal sinuses. The roles of the nasal sinuses include acting as breathing pathways, warming, humidifying, and filtering of inhaled air, olfaction, and being a resonant cavity, all of which are important for a comfortable life, and the loss of these functions reduces the quality of life. Therefore, to perform endoscopic endonasal skull base surgery in a minimally invasive and safe manner, it is necessary to understand the anatomy of the nasal sinuses to reach anterior skull base lesions while preserving nasal structures as much as possible. This article describes the normal local anatomy of the nasal cavity and the paranasal sinuses, as well as the surgical techniques, especially the anterior skull base approach and the pterygopalatine fossa approach, for endoscopic endonasal skull base surgery.