A rotatable operation device for an endoscope includes a fixed shaft projected outward from an operating portion, a cylindrical shaft projected from a rotatable operating member. The cylindrical shaft is rotatably fitted on the fixed shaft, and an end side surface of the cylindrical shaft contacts a fixed surface defined inside the operating portion. An internal space of the operating portion and an internal space of the rotatable operating member are airtight against outside. The rotatable operation device is configured to have an air passage which is formed in the cylindrical rotary shaft, a space at a fitted portion between the fixed shaft and the cylindrical rotary shaft communicating with the inside space of the operating portion through the air passage with the end side surface and the fixed surface remaining contacted.
