A device for sustained release of optical clearing agent includes a stick-shaped component having at least two supplying passages for supplying gas or liquid formed on the inside with 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 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, an optical clearing agent holding component fixed on the surface of one of the pouch-shaped elastic components and holding optical clearing agent, and a body-fluid absorbing component fixed on the surface of another one of the pouch-shaped elastic components and absorbing body fluid flowing from a target object or dehydrating the target object by osmotic pressure.