A medical instrument for observing the interior of a subject to be examined has an image pickup unit for picking up an image of the subject to be examined from a transparent cover member incorporated in the medical instrument, disposes a multi-bladed fan outside an image-pickup field of view of the image pickup unit, generates an airflow to an airflow outlet that causes the airflow to flow from the inlet port to the vicinity of an observation window, prevents adherents such as dirt from sticking to the cover member, prevents the adherents from sticking to the observation window of the observation apparatus without obstructing the field of view, and can thereby obtain a clear observed image.