An alkyloxirane derivative represented by formula (1), wherein MH and ML calculated from a gel permeation chromatogram satisfy formula (2): Z—[O-(AO)n-H]x  (1) where Z represents a residual group of a compound having 1 to 22 carbon atoms and one to six hydroxyl groups and wherein all of the hydroxyl groups are excluded from said compound; x is 1 to 6; and AO represents an oxyalkylene group having 3 carbon atoms; and n is 25 or more; 0.35≤ML/MH≤0.75  (2) where MH represents a distance between point O and intersecting point P, and ML represents a distance between point Q and intersecting point P determined from the chromatogram.