A hot water supply device comprising: a heat exchanger connected to a water supply pipe and a hot water supply pipe; a burner that heats the heat exchanger; a heat exchange outlet temperature sensor that detects a temperature of water in the heat exchanger or the hot water supply pipe in a vicinity of a place where the heat exchanger and the hot water supply pipe are connected; a running water sensor that detects for a presence of running water in the heat exchanger; a hot water supply controller that carries out a hot water supply operation in which the burner is turned on to heat water circulating in the heat exchanger in a case where running water is detected by the running water sensor, and turns the burner off to stop the hot water supply operation in a case where the running water is not detected by the running water sensor; and a heat exchange state determiner which, in a case where the hot water supply operation stops after the hot water supply operation is started in response to a predetermined instruction for checking a heat exchange state, carries out heat exchange success determination processing in which a post-boiling temperature indicating a rise width of a temperature detected by the heat exchange outlet temperature sensor from a time point at which the hot water supply operation stopped is measured, and the post-boiling temperature and a first threshold temperature are compared, and performs a predetermined successful heat exchange notification in a case where the post-boiling temperature is lower than the first threshold temperature, characterized in that the heat exchange state determiner carries out, in a case where the hot water supply operation stops after the hot water supply operation is started independently of the instruction for checking a heat exchange state, heat exchanger clogging determination processing in which the post-boiling temperature is measured and the post-boiling temperature is compared with a second threshold temperature, which is higher than the first threshold temperature, and performs a predetermined heat exchanger clogging notification in a case where the post-boiling temperature is higher than the second threshold temperature. a heat exchanger connected to a water supply pipe and a hot water supply pipe; a burner that heats the heat exchanger; a heat exchange outlet temperature sensor that detects a temperature of water in the heat exchanger or the hot water supply pipe in a vicinity of a place where the heat exchanger and the hot water supply pipe are connected; a running water sensor that detects for a presence of running water in the heat exchanger; a hot water supply controller that carries out a hot water supply operation in which the burner is turned on to heat water circulating in the heat exchanger in a case where running water is detected by the running water sensor, and turns the burner off to stop the hot water supply operation in a case where the running water is not detected by the running water sensor; and a heat exchange state determiner which, in a case where the hot water supply operation stops after the hot water supply operation is started in response to a predetermined instruction for checking a heat exchange state, carries out heat exchange success determination processing in which a post-boiling temperature indicating a rise width of a temperature detected by the heat exchange outlet temperature sensor from a time point at which the hot water supply operation stopped is measured, and the post-boiling temperature and a first threshold temperature are compared, and performs a predetermined successful heat exchange notification in a case where the post-boiling temperature is lower than the first threshold temperature, characterized in that the heat exchange state determiner carries out, in a case where the hot water supply operation stops after the hot water supply operation is started independently of the instruction for checking a heat exchange state, heat exchanger clogging determination processing in which the post-boiling temperature is measured and the post-boiling temperature is compared with a second threshold temperature, which is higher than the first threshold temperature, and performs a predetermined heat exchanger clogging notification in a case where the post-boiling temperature is higher than the second threshold temperature.