A monoclonal antibody having the ability of binding to CLD18A2 and mediating killing of cells expressing CLD18A2, wherein the antibody binds to an epitope localized on the CLD18A2-loop1 or the CLD18A2-loopD3 and wherein killing is induced by binding of the antibody to CLD18A2 expressed by said cells, wherein said antibody comprises a set of complementarity-determining regions CDR1, CDR2 and CDR3 selected from the following (i) to (ix): (i) VH: CDR1: positions 45-52 of SEQ ID NO: 115, CDR2: positions 70-77 of SEQ ID NO: 115, CDR3: positions 116-125 of SEQ ID NO: 115, VL: CDR1: positions 49-53 of SEQ ID NO: 122, CDR2: positions 71-73 of SEQ ID NO: 122, CDR3: positions 110-118 of SEQ ID NO: 122, (ii) VH: CDR1: positions 45-52 of SEQ ID NO: 116, CDR2: positions 70-77 of SEQ ID NO: 116, CDR3: positions 116-126 of SEQ ID NO: 116, VL: CDR1: positions 47-58 of SEQ ID NO: 121, CDR2: positions 76-78 of SEQ ID NO: 121, CDR3: positions 115-123 of SEQ ID NO: 121, (iii) VH: CDR1: positions 45-52 of SEQ ID NO: 117, CDR2: positions 70-77 of SEQ ID NO: 117, CDR3: positions 116-124 of SEQ ID NO: 117, VL: CDR1: positions 47-52 of SEQ ID NO: 123, CDR2: positions 70-72 of SEQ ID NO: 123, CDR3: positions 109-117 of SEQ ID NO: 123, (iv) VH: CDR1: positions 44-51 of SEQ ID NO: 119, CDR2: positions 69-76 of SEQ ID NO: 119, CDR3: positions 115-125 of SEQ ID NO: 119, VL: CDR1: positions 47-58 of SEQ ID NO: 126, CDR2: positions 76-78 of SEQ ID NO: 126, CDR3: positions 115-122 of SEQ ID NO: 126, (v) VH: CDR1: positions 45-52 of SEQ ID NO: 118, CDR2: positions 70-77 of SEQ ID NO: 118, CDR3: positions 116-126 of SEQ ID NO: 118, VL: CDR1: positions 47-58 of SEQ ID NO: 125, CDR2: positions 76-78 of SEQ ID NO: 125, CDR3: positions 115-123 of SEQ ID NO: 125, (vi) VH: CDR1: positions 45-53 of SEQ ID NO: 120, CDR2: positions 71-78 of SEQ ID NO: 120, CDR3: positions 117-128 of SEQ ID NO: 120, VL: CDR1: positions 47-58 of SEQ ID NO: 124, CDR2: positions 76-78 of SEQ ID NO: 124, CDR3: positions 115-123 of SEQ ID NO: 124, (vii) VH: CDR1: positions 45-53 of SEQ ID NO: 120, CDR2: positions 71-78 of SEQ ID NO: 120, CDR3: positions 117-128 of SEQ ID NO: 120, VL: CDR1: positions 47-58 of SEQ ID NO: 127, CDR2: positions 76-78 of SEQ ID NO: 127, CDR3: positions 115-123 of SEQ ID NO: 127, (viii) VH: CDR1: positions 45-53 of SEQ ID NO: 120, CDR2: positions 71-78 of SEQ ID NO: 120, CDR3: positions 117-128 of SEQ ID NO: 120, VL: CDR1: positions 47-58 of SEQ ID NO: 128, CDR2: positions 76-78 of SEQ ID NO: 128, CDR3: positions 115-123 of SEQ ID NO: 128, and (ix) VH: CDR1: positions 45-53 of SEQ ID NO: 120, CDR2: positions 71-78 of SEQ ID NO: 120, CDR3: positions 117-128 of SEQ ID NO: 120, VL: CDR1: positions 47-52 of SEQ ID NO: 129, CDR2: positions 70-72 of SEQ ID NO: 129, CDR3: positions 109-117 of SEQ ID NO: 129, and wherein said monoclonal antibody comprises a heavy chain variable region and a light chain variable region each composed of three CDRs. (i) VH: CDR1: positions 45-52 of SEQ ID NO: 115, CDR2: positions 70-77 of SEQ ID NO: 115, CDR3: positions 116-125 of SEQ ID NO: 115, VL: CDR1: positions 49-53 of SEQ ID NO: 122, CDR2: positions 71-73 of SEQ ID NO: 122, CDR3: positions 110-118 of SEQ ID NO: 122, (ii) VH: CDR1: positions 45-52 of SEQ ID NO: 116, CDR2: positions 70-77 of SEQ ID NO: 116, CDR3: positions 116-126 of SEQ ID NO: 116, VL: CDR1: positions 47-58 of SEQ ID NO: 121, CDR2: positions 76-78 of SEQ ID NO: 121, CDR3: positions 115-123 of SEQ ID NO: 121, (iii) VH: CDR1: positions 45-52 of SEQ ID NO: 117, CDR2: positions 70-77 of SEQ ID NO: 117, CDR3: positions 116-124 of SEQ ID NO: 117, VL: CDR1: positions 47-52 of SEQ ID NO: 123, CDR2: positions 70-72 of SEQ ID NO: 123, CDR3: positions 109-117 of SEQ ID NO: 123, (iv) VH: CDR1: positions 44-51 of SEQ ID NO: 119, CDR2: positions 69-76 of SEQ ID NO: 119, CDR3: positions 115-125 of SEQ ID NO: 119, VL: CDR1: positions 47-58 of SEQ ID NO: 126, CDR2: positions 76-78 of SEQ ID NO: 126, CDR3: positions 115-122 of SEQ ID NO: 126, (v) VH: CDR1: positions 45-52 of SEQ ID NO: 118, CDR2: positions 70-77 of SEQ ID NO: 118, CDR3: positions 116-126 of SEQ ID NO: 118, VL: CDR1: positions 47-58 of SEQ ID NO: 125, CDR2: positions 76-78 of SEQ ID NO: 125, CDR3: positions 115-123 of SEQ ID NO: 125, (vi) VH: CDR1: positions 45-53 of SEQ ID NO: 120, CDR2: positions 71-78 of SEQ ID NO: 120, CDR3: positions 117-128 of SEQ ID NO: 120, VL: CDR1: positions 47-58 of SEQ ID NO: 124, CDR2: positions 76-78 of SEQ ID NO: 124, CDR3: positions 115-123 of SEQ ID NO: 124, (vii) VH: CDR1: positions 45-53 of SEQ ID NO: 120, CDR2: positions 71-78 of SEQ ID NO: 120, CDR3: positions 117-128 of SEQ ID NO: 120, VL: CDR1: positions 47-58 of SEQ ID NO: 127, CDR2: positions 76-78 of SEQ ID NO: 127, CDR3: positions 115-123 of SEQ ID NO: 127, (viii) VH: CDR1: positions 45-53 of SEQ ID NO: 120, CDR2: positions 71-78 of SEQ ID NO: 120, CDR3: positions 117-128 of SEQ ID NO: 120, VL: CDR1: positions 47-58 of SEQ ID NO: 128, CDR2: positions 76-78 of SEQ ID NO: 128, CDR3: positions 115-123 of SEQ ID NO: 128, and (ix) VH: CDR1: positions 45-53 of SEQ ID NO: 120, CDR2: positions 71-78 of SEQ ID NO: 120, CDR3: positions 117-128 of SEQ ID NO: 120, VL: CDR1: positions 47-52 of SEQ ID NO: 129, CDR2: positions 70-72 of SEQ ID NO: 129, CDR3: positions 109-117 of SEQ ID NO: 129,