The present invention provides an anti-LAG-3 antibody capable of repeated administration even to animals other than rat. An anti-LAG-3 antibody comprising (a) a light chain comprising a light chain variable region containing CDR1 having the amino acid sequence of QSLLDSDGNTY (SEQ ID NO: 16), CDR2 having the amino acid sequence of SVS and CDR3 having the amino acid sequence of MQATHVPFT (SEQ ID NO: 17) and the light chain constant region of an antibody of an animal other than rat； and (b) a heavy chain comprising a heavy chain variable region containing CDR1 having the amino acid sequence of GFDFDTYP (SEQ ID NO: 18), CDR2 having the amino acid sequence of ITIKTHNYAT (SEQ ID NO: 19) and CDR3 having the amino acid sequence of NREDFDY (SEQ ID NO: 20) and the heavy chain constant region of an antibody of an animal other than rat. A pharmaceutical composition comprising the above anti-LAG-3 antibody as an active ingredient. A method for preparing the above anti-LAG-3 antibody is also provided.
