The present disclosure relates to a boiler for making hot water and room heating water available simultaneously, which is capable of enabling a user to use hot water and room heating simultaneously. According to the present disclosure, a thermal loss of room heating water may be minimized because the room heating water is independently supplied to a room heating pipe and returned regardless of the use of hot water, and the hot water with a high temperature may be consistently supplied because the hot water is independently supplied to a hot water pipe and returned regardless of the use of the room heating water. In addition, the boiler may serve as both a hot-water heat exchanger and a distributor (low loss header).