The present invention relates a novel cell-killing peptide, particularly to a cell-killing peptide that exploits a specific region at the C-terminus of Noxa protein, a BH3-only member of Bcl-2 family causing apoptosis and fusion proteins containing the same. According to the present invention, the cell-killing peptide (CKP) effectively kills a cancer cell such as HeLa or HCT116 when it is conjugated with PTD or CTD domain. Therefore, the cell-killing peptide of the present invention is still stronger to kill cells, compared with conventional substances such as TRAIL, and will be applied widely for various cell therapies, especially in cancer treatment.