An endoscope apparatus is provided that includes a plurality of kinds of optical adapters that have an illuminating window and an observation window, and an endoscope insertion portion that has a distal end portion to which the plurality of kinds of optical adapters can be detachably attached. A fluid spout that ejects fluid at least at the observation window, and a fluid inlet whose arrangement position is common among the plurality of kinds of optical adapters and that is connected to and communicates with a fluid supply port for supplying the fluid that is arranged on a distal end face of the distal end portion are provided in the optical adapters. A fluid supply channel that causes the fluid inlet and the fluid spout to communicate and in which the fluid flows and the fluid spout are configured differently according to the kind of the optical adapter.
