A process for hydrotreating a naphtha fraction, comprising: a naphtha fraction hydrotreating step of hydrotreating a naphtha fraction in a naphtha fraction hydrotreating reactor, wherein the naphtha fraction is contained within the hydrocarbon compounds synthesized in a Fischer-Tropsch synthesis reactor a naphtha fraction discharge step of discharging the napthta fraction treated in the naphtha fraction hydrotreating reactor, a naphtha fraction return step of returning a portion of the naphtha fraction discharged from the naphtha fraction hydrotreating reactor to the naphtha fraction hydrotreating reactor to form a mixed naphtha fraction, wherein the process is characterized by comprising: a reactor temperature difference estimation step of estimating a difference between the outlet temperature and inlet temperature of the naphtha fraction hydrotreating reactor by estimating the amount of heat generated in the naphtha fraction hydrotreating step per unit volume of the mixed naphtha fraction under the assumption that the conversion of the olefins and alcohols is 100%, and taking into account the reaction temperature of the Fischer-Tropsch synthesis reactor, and the ratio of the flow rate of the treated naphtha fraction returned to the naphtha fraction hydrotreating reactor relative to the flow rate of the treated naphtha fraction discharged from the naphtha fraction hydrotreating reactor, a reactor temperature difference measurement step of measuring the actual difference between the naphtha fraction hydrotreating reactor outlet temperature and inlet temperature, and a reaction temperature adjustment step of adjusting the reaction temperature in the naphtha fraction hydrotreating reactor so that the difference between the outlet temperature and inlet temperature of the naphtha fraction hydrotreating reactor, which is measured in the reactor temperature difference measurement step becomes substantially equal to the difference estimated in the reactor temperature difference estimation step under the assumption that the conversion of the olefins and alcohols is 100%. a naphtha fraction hydrotreating step of hydrotreating a naphtha fraction in a naphtha fraction hydrotreating reactor, wherein the naphtha fraction is contained within the hydrocarbon compounds synthesized in a Fischer-Tropsch synthesis reactor a naphtha fraction discharge step of discharging the napthta fraction treated in the naphtha fraction hydrotreating reactor, a naphtha fraction return step of returning a portion of the naphtha fraction discharged from the naphtha fraction hydrotreating reactor to the naphtha fraction hydrotreating reactor to form a mixed naphtha fraction, wherein the process is characterized by comprising: a reactor temperature difference estimation step of estimating a difference between the outlet temperature and inlet temperature of the naphtha fraction hydrotreating reactor by estimating the amount of heat generated in the naphtha fraction hydrotreating step per unit volume of the mixed naphtha fraction under the assumption that the conversion of the olefins and alcohols is 100%, and taking into account the reaction temperature of the Fischer-Tropsch synthesis reactor, and the ratio of the flow rate of the treated naphtha fraction returned to the naphtha fraction hydrotreating reactor relative to the flow rate of the treated naphtha fraction discharged from the naphtha fraction hydrotreating reactor, a reactor temperature difference measurement step of measuring the actual difference between the naphtha fraction hydrotreating reactor outlet temperature and inlet temperature, and a reaction temperature adjustment step of adjusting the reaction temperature in the naphtha fraction hydrotreating reactor so that the difference between the outlet temperature and inlet temperature of the naphtha fraction hydrotreating reactor, which is measured in the reactor temperature difference measurement step becomes substantially equal to the difference estimated in the reactor temperature difference estimation step under the assumption that the conversion of the olefins and alcohols is 100%. a reactor temperature difference estimation step of estimating a difference between the outlet temperature and inlet temperature of the naphtha fraction hydrotreating reactor by estimating the amount of heat generated in the naphtha fraction hydrotreating step per unit volume of the mixed naphtha fraction under the assumption that the conversion of the olefins and alcohols is 100%, and taking into account the reaction temperature of the Fischer-Tropsch synthesis reactor, and the ratio of the flow rate of the treated naphtha fraction returned to the naphtha fraction hydrotreating reactor relative to the flow rate of the treated naphtha fraction discharged from the naphtha fraction hydrotreating reactor, a reactor temperature difference measurement step of measuring the actual difference between the naphtha fraction hydrotreating reactor outlet temperature and inlet temperature, and a reaction temperature adjustment step of adjusting the reaction temperature in the naphtha fraction hydrotreating reactor so that the difference between the outlet temperature and inlet temperature of the naphtha fraction hydrotreating reactor, which is measured in the reactor temperature difference measurement step becomes substantially equal to the difference estimated in the reactor temperature difference estimation step under the assumption that the conversion of the olefins and alcohols is 100%.