Five novel amphoteric surfactants of N-acyloxyethylcarboxybetaine series were synthesized via Schotten-Baumman reaction between five acid chlorides containing 10, 12, 14, 16 and 18 carbon atoms in their N-alkyl groups and dimethylaminoethanol to give the intermediate products, 2-dimethylaminoethylalkanoates(2). Quaternization of these products(2) was permitted to from 2-(acyloxyethyldimethylammonic)- acetates(3), whose structures were identified by elemental analysis, IR spectrophotometry and $^1Hnmr$ spectrometry. The yield of the final products was shown in the range of 77-80% based on the intermediate products. The surface tension of the aqueous solution of (3) was measured, and the critical micelle concentrations (cmc) were shown in the range of $2.1;{ imes};10^{-3};-;3.3;{ imes};10^{-4}mol/l$, and the surface tension at cmc was 28-36 dyne/cm. Cmc was lowered gradually by the increment of the length of N-alkyl ester containing group. The isoelectric point was shown in the range of 4.44-5.20. It showed a tendency to lean toward the acidic site and its range was broadened as increase of the hydrophobic group length. A linear relationship between log cmc and the number of carbon atoms(N) in the hydrophobic alkyl chain was shown in the relative equation of log cmc=-1.75-0.1N, and the contribution rate of N on the standard free energy change in micellization, ${igtriangleup}({igtriangleup}G^{circ}m)/{igtriangleup}N$, was calculated as -0.23 RT.