The present invention relates to an antibody against PD-L1 (Programmed death-ligand 1) or an antigen-binding fragment thereof, a nucleic acid encoding the same, a vector containing the nucleic acid, a cell transformed with the vector, the antibody or the antigen-binding fragment thereof The present invention relates to a production method and a composition for preventing or treating cancer or infectious diseases including the same. [Selection] Figure 1本発明はPD-L1(Programmed death-ligand 1)に対する抗体又はその抗原結合断片、これをコードする核酸、該核酸を含むベクター、該ベクターで形質転換された細胞、前記抗体又はその抗原結合断片の製造方法及びこれを含む癌又は感染疾患の予防又は治療用組成物に関する。【選択図】図1