Ethoxylated fatty alcohol is a mosquito larvicide and pupicide belonging to the chemical class of compounds known as nonionic surfactants. It was tested on evaluations of mosquito control effect against larvae and pupae of Aedes togoi in a laboratory. In larval experiment, mortality rates of 3rd instar larvae were only below 32.0% at dosages of 0.4, 0.8, 1.6, 3.2 and 6.4 ml/$m^2$ until 7 days after treatment. However, the mortality rates of the pupae were 86.5% at 0.4 ml/$m^2$ and 95.0% at 6.4 ml/$m^2$. In pupal stage of Ae. togoi, mortality rates appeared sensitively to the dosage of ethoxylated fatty alcohol compare with larvae. The dosage of 0.02 ml/$m^2$ was the lowest volume to control Ae. togoi as 96.0% within 1 day and 100.0% of total control of pupae within 2 days after treatment in fresh water of the experimental condition. However, the mortality rates of the pupae were sharply decreased after 8 days and pupal control were from 0.0% at 0.02 ml/$m^2$ to 7.2% at 0.04 ml/$m^2$ although mortality rates were much higher at 0.32 ml/$m^2$ (98.6%) which was 8 times higher dosage than 0.04 ml/$m^2$. The high residual activity of ethoxylated fatty alcohol did not continue from an 8 day group after treatment which was from the mortality rates of 0.0 % at 0.02 ml/$m^2$ to 46.4 % at 0.08 ml/$m^2$. It is concluded that ethoxylated fatty alcohol might be useful to control Ae. togoi pupae at over 0.02 ml/$m^2$ for two days, and the dosages for successive control might be 0.16 and 0.32 ml/$m^2$against Ae. togoi for at least 4 and 15 days, respectively.