An endoscope apparatus includes: an endoscope including a first operation portion that is coupled to a first insertion portion to be inserted into a subject; a medical device including a second operation portion that is coupled to a second insertion portion to be inserted into the subject through the first insertion portion, the second operation portion including at least one locking member; and a belt-like body having flexibility and including at least three end portions in which at least one end portion includes a locked portion to be locked to the locking portion, the belt-like body being configured to be wound around the endoscope to hold and fix the second operation portion of the medical device in a state where the at least three end portions are connected to the second operation portion.