A storage-type hot-water supplying system comprising: a heat source unit a plurality of hot-water storage tanks (7A, 7B, 7C) connected in series and provided between a hot-water outlet pipe for high-temperature water, extending from the heat source unit, and a water supplying pipe for low-temperature water, leading to the heat source unit, wherein the storage-type hot-water supplying system is configured to sequentially supply high temperature water stored in the plurality of the hot-water storage tanks (7A, 7B, 7C) to a load, wherein, of the plurality of hot-water storage tanks (7A, 7B, 7C), the most-upstream hot-water storage tank, extending from the heat source unit, serves as a hot-water-supplying hot-water storage tank for high-temperature water, and a most-downstream hot-water storage tank serves as a water-supplying hot-water storage tank for the heat source unit, characterized in that the storage-type hot-water supplying system further comprises a mixing valve (10B, 10C) that is connected to a top portion of at least one of the hot-water storage tanks (7B, 7C) at a downstream side of a most-upstream hot-water-supplying hot-water storage tank that is closest to the hot-water outlet pipe, and wherein a hot-water supplying system for high-temperature water is connected to the most-upstream hot-water-supplying hot-water storage tank, and at least one hot-water supplying system (9B, 9C) that allows hot water of different temperatures to be supplied via the mixing valve (10B, 10C) is connected to a top portion of at least one of the hot-water storage tanks (7B, 7C) at a downstream side of the most-upstream hot-water-supplying hot-water storage tank. a heat source unit a plurality of hot-water storage tanks (7A, 7B, 7C) connected in series and provided between a hot-water outlet pipe for high-temperature water, extending from the heat source unit, and a water supplying pipe for low-temperature water, leading to the heat source unit, wherein the storage-type hot-water supplying system is configured to sequentially supply high temperature water stored in the plurality of the hot-water storage tanks (7A, 7B, 7C) to a load, wherein, of the plurality of hot-water storage tanks (7A, 7B, 7C), the most-upstream hot-water storage tank, extending from the heat source unit, serves as a hot-water-supplying hot-water storage tank for high-temperature water, and a most-downstream hot-water storage tank serves as a water-supplying hot-water storage tank for the heat source unit, wherein the storage-type hot-water supplying system is configured to sequentially supply high temperature water stored in the plurality of the hot-water storage tanks (7A, 7B, 7C) to a load, wherein, of the plurality of hot-water storage tanks (7A, 7B, 7C), the most-upstream hot-water storage tank, extending from the heat source unit, serves as a hot-water-supplying hot-water storage tank for high-temperature water, and a most-downstream hot-water storage tank serves as a water-supplying hot-water storage tank for the heat source unit, characterized in that the storage-type hot-water supplying system further comprises a mixing valve (10B, 10C) that is connected to a top portion of at least one of the hot-water storage tanks (7B, 7C) at a downstream side of a most-upstream hot-water-supplying hot-water storage tank that is closest to the hot-water outlet pipe, and wherein a hot-water supplying system for high-temperature water is connected to the most-upstream hot-water-supplying hot-water storage tank, and at least one hot-water supplying system (9B, 9C) that allows hot water of different temperatures to be supplied via the mixing valve (10B, 10C) is connected to a top portion of at least one of the hot-water storage tanks (7B, 7C) at a downstream side of the most-upstream hot-water-supplying hot-water storage tank.