The present invention offers a means for sustained release of optical clearing agent making it possible to shorten necessary time for obtaining an effect of making a living tissue transparent with physical burden on the living tissue and work burden reduced and making it possible to stably give optical clearing agent also to a target region located at a position in the opposite direction to the direction of gravity, an endoscope having the same, and an instrument for endoscopic surgery having the same. The means for sustained release of optical clearing agent includes a stick-shaped component 1 with at least two supplying passages 2 and 3 for supplying gas or liquid, the supplying passages being formed on the inside of the stick-shaped component and apertures of the supplying passages being formed at positions along the circumference of the lateral surface in the vicinity of the top end of the stick-shaped component respectively, at least two pouch-shaped elastic components 5 and 6 placed at positions along the circumference of the lateral surface in the vicinity of the top end of the stick-shaped component respectively to cover the apertures of the supplying passages respectively, the pouched-shaped elastic components being capable of being controlled to inflate or deflate in accordance with an amount of an inflow of or an outflow of the gas or liquid, an optical clearing agent holding component 7 fixed on the surface of the first component 5 of the pouch-shaped elastic components, the optical clearing agent holding component holding the optical clearing agent and the optical clearing agent holding component being pressed to perform sustained release of the optical clearing agent to the outside, and a body-fluid absorbing component 8 fixed on the surface of the second component 6 of the pouch-shaped elastic components, the body-fluid absorbing component absorbing body fluid which flows from a target object for sustained release of the optical clearing agent or the
