A hot-water supply system comprising: a heating unit configured to produce high-temperature water by heating low-temperature water; and at least one hot-water storage tank that is connected to the heating unit via a low-temperature water pipe and a high-temperature water pipe and that is configured to sequentially store the high-temperature water produced in the heating unit, forming a temperature stratification from a top side of the hot-water storage tank, wherein the hot-water supply system is capable of maintaining temperature of hot water stored in the hot-water storage tank after completion of storing hot water at a set temperature, wherein a plurality of temperature sensors (21A, 21B, 21N) are provided to be mutually apart in a vertical direction in the hot-water storage tank, and the temperature sensor provided at the lowest level therein is a first temperature sensor that detects a situation that the hot water with the set temperature is stored to a 100% level, the hot-water supply system further comprising: a control unit that is configured to control the operation and stopping of the heating unit during a heating-up operation and an additional heating operation on the basis of a detected value from the first temperature sensor, characterized in that during the additional heating operation, when the detected value from the first temperature sensor reaches a set temperature, the control unit is configured to correct the set temperature of the first temperature sensor based on a temperature difference ΔT-ΔT' between a detected value ΔT' from a second temperature sensor (21B, 21N) provided above the first temperature sensor and a detected value ΔT that the second temperature sensor detects during the heating-up operation, and the control unit is configured to control the operation and stopping of the heating unit with the corrected value which serves as a target temperature. a heating unit configured to produce high-temperature water by heating low-temperature water; and at least one hot-water storage tank that is connected to the heating unit via a low-temperature water pipe and a high-temperature water pipe and that is configured to sequentially store the high-temperature water produced in the heating unit, forming a temperature stratification from a top side of the hot-water storage tank, wherein the hot-water supply system is capable of maintaining temperature of hot water stored in the hot-water storage tank after completion of storing hot water at a set temperature, wherein a plurality of temperature sensors (21A, 21B, 21N) are provided to be mutually apart in a vertical direction in the hot-water storage tank, and the temperature sensor provided at the lowest level therein is a first temperature sensor that detects a situation that the hot water with the set temperature is stored to a 100% level, the hot-water supply system further comprising: a control unit that is configured to control the operation and stopping of the heating unit during a heating-up operation and an additional heating operation on the basis of a detected value from the first temperature sensor, characterized in that during the additional heating operation, when the detected value from the first temperature sensor reaches a set temperature, the control unit is configured to correct the set temperature of the first temperature sensor based on a temperature difference ΔT-ΔT' between a detected value ΔT' from a second temperature sensor (21B, 21N) provided above the first temperature sensor and a detected value ΔT that the second temperature sensor detects during the heating-up operation, and the control unit is configured to control the operation and stopping of the heating unit with the corrected value which serves as a target temperature. a control unit that is configured to control the operation and stopping of the heating unit during a heating-up operation and an additional heating operation on the basis of a detected value from the first temperature sensor, characterized in that during the additional heating operation, when the detected value from the first temperature sensor reaches a set temperature, the control unit is configured to correct the set temperature of the first temperature sensor based on a temperature difference ΔT-ΔT' between a detected value ΔT' from a second temperature sensor (21B, 21N) provided above the first temperature sensor and a detected value ΔT that the second temperature sensor detects during the heating-up operation, and the control unit is configured to control the operation and stopping of the heating unit with the corrected value which serves as a target temperature.