A system for managing a temperature of a urea solution configured to thaw or keep warm a urea solution stored in a urea solution tank by flowing a heating medium to pass through the urea solution tank, the urea solution tank storing the urea solution to be used as a reducing agent for NOx purification treatment in an exhaust gas of an internal combustion engine, wherein a control device is configured to control a flow control valve that is configured to regulate a flow rate of the heating medium to be supplied to the urea solution tank, the control device being configured to perform control of: setting a valve-open time ratio of the flow control valve, which is a value calculated by setting a preset unit control time period (Rt) as a denominator and a valve opening time period (Ra) over which the flow control valve is opened during the unit control time period as a numerator, expressed as a percentage, to 100% so as to make the flow control valve continuously open when a temperature of the urea solution in the urea solution tank is equal to or lower than a preset first temperature, characterised by setting the valve-open time ratio of the flow control valve to a preset set ratio when the temperature of the urea solution in the urea solution tank is a preset second temperature; setting the valve-open time ratio of the flow control valve to 0% so as to make the flow control valve continuously close when the temperature of the urea solution in the urea solution tank is equal to or higher than a preset third temperature; setting the valve-open time ratio of the flow control valve to a linearly interpolated time ratio between 100% and the set ratio when the temperature of the urea solution in the urea solution tank is between the first temperature and the second temperature; and setting the valve-open time ratio of the flow control valve to a linearly interpolated time ratio between the set ratio and 0% when the temperature of the urea solution in the urea solution tank is between the second temperature and the third temperature. setting a valve-open time ratio of the flow control valve, which is a value calculated by setting a preset unit control time period (Rt) as a denominator and a valve opening time period (Ra) over which the flow control valve is opened during the unit control time period as a numerator, expressed as a percentage, to 100% so as to make the flow control valve continuously open when a temperature of the urea solution in the urea solution tank is equal to or lower than a preset first temperature, characterised by setting the valve-open time ratio of the flow control valve to a preset set ratio when the temperature of the urea solution in the urea solution tank is a preset second temperature; setting the valve-open time ratio of the flow control valve to 0% so as to make the flow control valve continuously close when the temperature of the urea solution in the urea solution tank is equal to or higher than a preset third temperature; setting the valve-open time ratio of the flow control valve to a linearly interpolated time ratio between 100% and the set ratio when the temperature of the urea solution in the urea solution tank is between the first temperature and the second temperature; and setting the valve-open time ratio of the flow control valve to a linearly interpolated time ratio between the set ratio and 0% when the temperature of the urea solution in the urea solution tank is between the second temperature and the third temperature.