A reactive vesicle comprising, as a vesicle-forming component, a reactive phospholipid derivative represented by the following general formula (1) and a functional substance-fixed vesicle prepared by reacting the reactive vesicle with a functional substance: ##STR1## in which R.sup.1 C(.dbd.O) and R.sup.2 C(.dbd.O) each represent an aliphatic acyl group, R.sup.3 denotes hydrogen atom or methyl group, OA represents an oxyalkylene group of 2-4 carbon atoms, n indicates the average number of moles of added oxyalkylene group and is 1-1,000, p is 0 or 1, X represents ##STR2## with q and r each being an integer of 0 to 4 or 1 to 4, respectively, and M denotes hydrogen atom or an alkli metal atom.