Provided is a polymersome composition that has skin disorder remedying effects, that is safe, that provides a pleasant feel upon use and a fresh feel without any stickiness, and that has excellent base-agent stability. The disclosed polymersome contains, as a membrane component, a block-type alkylene oxide derivative represented by the following formula (I): R1O-[(EO)l(AO)m(EO)n]-R2. (In the formula, AO represents an oxyalkylene group having 3 or 4 carbons； EO represents an oxyethylene group； m represents an average addition mole number of the oxyalkylene group and satisfies 1=m=70； and 1+n represents an average addition mole number of the oxyethylene group and satisfies 1=1+n=70. The percentage of the oxyethylene group to the sum of the oxyalkylene group having 3 or 4 carbons and the oxyethylene group is 20% to 80% by mass. The oxyalkylene group having 3 or 4 carbons and the oxyethylene group are added blockwise. R1 and R2 each represent a hydrocarbon group having 1 to 4 carbons, which may be the same or different from each other.)
