A basic agent for use in cosmetics comprising an alkylene oxide derivative represented by the following formula (I) is provided: Z-{O(AO)l(EO)m - (BO)nH}a (I)(where Z represents a residue of a compound having 3 to 9 hydroxyl groups with the hydroxyl groups removed, a is from 3 to 9, AO represents an oxyalkylene group of 3 to 4 carbon atoms, EO represents oxyethylene group, l and m represent average additional mol numbers of the oxyalkylene groups of 3 to 4 carbon atoms and the oxyethylene groups, respectively, and 1 ≦1 ≦50, 1 ≦ m ≦50, the weight ratio (AO/EO) of AO to EO is from 1/5 to 5/1, AO and EO may be added in a random form or may be added in a block form. BO represents oxyalkylene group with a number of carbon atoms of 4, and n is an average additional mol number and 0.5 ≦ n ≦ 5).
