Critical micelle concentration (CMC) of lecithin and lysolecithin was measured according to the electric conductivity method and the fluorescence method. Lecithin presented no distinct CMC in either alcohol solution or water suspension, but lysolecithin showed clear CMC by those two methods as follows : 0.08×10^-4 mol in water at 20°C, 0.62×10^-4 M in water at 30°C and 0.125×10^-4mol in alcohol at room temperature by the measurement of electric conductivity, and 0.125×10^-4mol in water, 0.14×10^-4mol in alcohol both at room temperature by the fluorescence method.