A power supply unit having a load which is able to heat an aerosol source and whose electric resistance value has correlation with a temperature thereof and a power supply capable of discharging electricity to the load, the power supply unit further comprising: a first branch circuit that includes the load, a first known resistor, and a first node connecting the load and the first known resistor in series; a second branch circuit that includes a second known resistor, a third known resistor, and a second node connecting the second known resistor and the third known resistor in series, the second branch circuit being connected in parallel with the first branch circuit; an operational amplifier of which the non-inverting input terminal is connected to one of the first node and the second node, and of which the inverting input terminal is connected to the other of the first node and the second node; and characterised by a control device having an upper limit temperature for stopping heating the load and a lower limit temperature for not allowing electricity discharge to the load, wherein the electric resistance value of the first known resistor, the electric resistance value of the load, the electric resistance value of the second known resistor, and the electric resistance value of the third known resistor are electric resistance values that satisfy a first condition and a second condition, wherein the first condition is that the differential input of the operational amplifier is larger than the potential of the negative power supply terminal of the operational amplifier or a minimum value that is acquirable by the operational amplifier, in a first temperature range including the upper limit temperature, and wherein the second condition is that the differential input of the operational amplifier is equal to the potential of the negative power supply terminal of the operational amplifier or the minimum value that is acquirable by the operational amplifier, in a second temperature range including the lower limit temperature and being different from the first temperature range. a first branch circuit that includes the load, a first known resistor, and a first node connecting the load and the first known resistor in series; a second branch circuit that includes a second known resistor, a third known resistor, and a second node connecting the second known resistor and the third known resistor in series, the second branch circuit being connected in parallel with the first branch circuit; an operational amplifier of which the non-inverting input terminal is connected to one of the first node and the second node, and of which the inverting input terminal is connected to the other of the first node and the second node; and characterised by a control device having an upper limit temperature for stopping heating the load and a lower limit temperature for not allowing electricity discharge to the load, wherein the electric resistance value of the first known resistor, the electric resistance value of the load, the electric resistance value of the second known resistor, and the electric resistance value of the third known resistor are electric resistance values that satisfy a first condition and a second condition, wherein the first condition is that the differential input of the operational amplifier is larger than the potential of the negative power supply terminal of the operational amplifier or a minimum value that is acquirable by the operational amplifier, in a first temperature range including the upper limit temperature, and wherein the second condition is that the differential input of the operational amplifier is equal to the potential of the negative power supply terminal of the operational amplifier or the minimum value that is acquirable by the operational amplifier, in a second temperature range including the lower limit temperature and being different from the first temperature range.