Disclosed are improved peptides for inhibiting angiogenesis, Ac-RLYE (SEQ ID NO: 1) and R(D)LYE (SEQ ID NO: 6), and a composition for the prevention and treatment of cancers and diseases related to angiogenesis comprising the peptides as an active ingredient. A peptide for inhibiting angiogenesis is disclosed wherein the L-Arg of an N-terminal is acetylated in a peptide consisting of an amino acid sequence of Arg-Leu-Tyr-Glu (SEQ ID NO: 1). A peptide for inhibiting angiogenesis is disclosed wherein L-Arg is substituted with D-Arg in a peptide consisting of the amino acid sequence of Arg-Leu-Tyr-Glu (SEQ ID NO: 6). Methods for using a composition comprising the peptides as active ingredients for the prevention or treatment of diseases (cancer, diabetic retinopathy or senile macular degeneration) caused by excessive angiogenesis are also disclosed. The peptides have a long half-life and are excellent in VEGF-induced angiogenesis inhibitory effect.