The invention relates to a check valve for a small sized hot-water boiler capable of preventing noise. A left inner tube and a left outer tube are arranged around the left outside of a cylindrical body as a double layer surrounding structure with a certain interval. The water of water tank passes between the outer surface of the left inner tube and the inner surface of the left outer tube, and circulates like a ''z'' character between the inner surface of the left inner tube and the outer surface of the check valve cylindrical body. A right inner tube and a right outer tube are arranged around the right side of the cylindrical body as a double layer surrounding structure with a certain interval. The fast expand hot water which is heated by a heater cylinder passes between the outer surface of an inward tube connection opening in the right outer tube center and the inner surface of the right inner tube, and circulates like a ''z'' character between the outer surface of the right inner tube and the inner surface of the cylindrical body, thereby minimizing the circulation pressure of the water from the water tank and the hot water from the heater heater cylinder and forming a double water layers, and preventing the opening and closing noise in the check valve from speading outward.