A liquid-dispensing structure includes: an outer cylinder with a one-way valve at its lower end to allow a liquid to flow into the outer cylinder; a hollow piston being slidable inside the outer cylinder and having a pair of liquid-tight portions formed with circular convex portions around its outer circumferential surface in positions apart in an axial direction; and an inner cylinder for dispensing a liquid, which reciprocates inside the outer cylinder so that the piston moves in a piston-sliding area of the inner cylinder having an opening through which the liquid flows. The opening is closed when the piston is at a lower position and is opened when the piston is at an upper position.