A control device for controlling a warm water heating system, the control device comprising: a heat pump including a heat output heat exchanger which takes heat from a heat source system and outputs heat; a heating portion which heats water using the heat obtained from the heat output heat exchanger; an outflow portion which flows the water heated by the heating portion to a heating target; a circulation portion which circulates the water heated by the heating portion to an upstream side of the heating portion; an inflow portion which flows water from the heating target into the upstream side of the heating portion; and an adjustment unit which adjusts flow amount distribution of the water from the heating portion to the outflow portion and the circulation portion, characterized in that the control device includes an upstream-side target temperature setting unit which sets a target temperature of the water on the upstream side of the heating portion; and an adjustment amount determination unit which determines an adjustment amount of the flow amount distribution by the adjustment unit so that a temperature of the water on the upstream side of the heating portion increases by a predetermined temperature until the temperature of the water on the upstream side of the heating portion reaches the target temperature, and wherein the adjustment amount determination unit determines the adjustment amount of the flow amount distribution by the adjustment unit so that the temperature of the water on the upstream side of the heating portion increases by a predetermined temperature calculated based on states of water flowing in the heating portion, water circulated by the circulation portion, and water flowing from the inflow portion into the upstream side of the heating portion until the temperature of the water on the upstream side of the heating portion reaches the target temperature. a heat pump including a heat output heat exchanger which takes heat from a heat source system and outputs heat; a heating portion which heats water using the heat obtained from the heat output heat exchanger; an outflow portion which flows the water heated by the heating portion to a heating target; a circulation portion which circulates the water heated by the heating portion to an upstream side of the heating portion; an inflow portion which flows water from the heating target into the upstream side of the heating portion; and an adjustment unit which adjusts flow amount distribution of the water from the heating portion to the outflow portion and the circulation portion, characterized in that the control device includes an upstream-side target temperature setting unit which sets a target temperature of the water on the upstream side of the heating portion; and an adjustment amount determination unit which determines an adjustment amount of the flow amount distribution by the adjustment unit so that a temperature of the water on the upstream side of the heating portion increases by a predetermined temperature until the temperature of the water on the upstream side of the heating portion reaches the target temperature, and wherein the adjustment amount determination unit determines the adjustment amount of the flow amount distribution by the adjustment unit so that the temperature of the water on the upstream side of the heating portion increases by a predetermined temperature calculated based on states of water flowing in the heating portion, water circulated by the circulation portion, and water flowing from the inflow portion into the upstream side of the heating portion until the temperature of the water on the upstream side of the heating portion reaches the target temperature.