A heating and hot-water-supply apparatus is provided with: a control unit that performs control on the basis of detection parameters of a plurality of detection means installed at the aforementioned locations and a setting parameter set in an operation unit. The distribution means can adjust the distribution ratio so as to correspond to a heating operation, a hot-water supply operation, and the simultaneous heating and hot-water-supply operation. The control unit prohibits the simultaneous heating and hot-water-supply operation in a case in which the required heating capacity for the hot-water supply operation calculated on the basis of the detection parameters and the setting parameter is equal to or greater than a predetermined standard capacity.