The utility model relates to a condenser, which comprises a casing, wherein a steam inlet and outlet and a condensed water outlet are arranged on the casing, and an inner cavity of the casing is divided into a steam chamber and a water chamber by a partition board. The steam inlet and outlet and the condensed water outlet are communicated with the steam chamber. A cooling water tube bundle is arranged in the steam chamber and divided into at least two parts (3 and 4; 5, 6 and 7), each part of the cooling water tube bundle is respectively provided with water inlet pipes and water outlet pipes, the water inlet pipes of each part of the cooling water tube bundle are communicated with cooling water inlets of the water chamber, and the water outlet pipes of each part of the cooling water tube bundle are communicated with corresponding cooling water outlets of the water chamber. As to each part of the cooling water tube bundle, the cooling water outlets corresponding to the part of the cooling water tube bundle and the cooling water outlets corresponding to other part of the cooling water tube bundle are separated from each other. Provided are also a heat-supply system and a condensed water heating system which both contain the condenser. The condenser, the heat-supply system and the condensed water heating system enable waste heat of circulating cooling water in a power station to be used, and are simple in structure and low in cost.