A phospholipid derivative represented by the formula (1) (Z represents a residue of a compound having 3 to 10 hydroxyl groups; AO represents an oxyalkylene group having 2 to 4 carbon atoms; R.sup.1CO and R.sup.2CO represent an acyl group having 8 to 22 carbon atoms; X represents hydrogen atom, an alkali metal atom, ammonium or an organic ammonium; "a" represents an integer of 0 to 4; "b" represents 0 or 1; Q represents hydrogen atom or methyl group; m represents an average number of moles of the oxyalkylene group added; and m, k1, k2, and k3 are numbers satisfying the following conditions: 3.ltoreq.m.ltoreq.200, 9.ltoreq.m.times.(k1+k2+k3).ltoreq.1000, 1.ltoreq.k1.ltoreq.2, 0.ltoreq.k2.ltoreq.9 and 0.ltoreq.k3.ltoreq.9, and 3.ltoreq.k1+k2+k3.ltoreq.10), which is highly safe for living bodies, and is suitably used for solubilization and dispersion of physiologically active substances and the like, or in the fields of drug delivery systems such as liposomes and cosmetics. ##STR00001##