98% sodium hydroxide 108.535 mmol and methanol 38.74g were introduced into a 200mL eggplant flask which was equipped with a Dimroth condenser, the mixture was stirred at 50 °C until sodium hydroxide was dissolved. Sodium hydroxide amount to 1 liter of methanol in this case was 2.17 mol. After the sodium hydroxide had dissolved 1H, 1H, 2H, 2H-1-iodoperfluorodecane 104.996mmol was charged and further stirred for 2 hours at 50 °C. Heating and stirring were stopped, the obtained two-layer solution which became slightly pale brown turbid was separated after standing, and 45.81g lower layer was collected as 1H,1H,2H-perfluorodecene. As a result of analysis by gas chromatography, purity was 98.59%. The weight of the separated methanol layer was 56.10g.