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<1>CO and R<2>CO 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
