Provided is an anti-LAG-3 antibody that can be frequently administered to a non-rat animal. The anti-LAG-3 antibody comprises: (a) an L chain comprising an L-chain variable region that includes CDR1 having a QSLLDSDGNTY (SEQ ID NO. 16) amino acid sequence, CDR2 having an SVS amino acid sequence, and CDR3 having an MQATHVPFT (SEQ ID NO. 17) amino acid sequence, and an L-chain constant region of a non-rat mammalian antibody； and (b) an H chain comprising an H-chain variable region that includes CDR1 having a GFDFDTYP (SEQ ID NO. 18) amino acid sequence, CDR2 having an ITIKTHNYAT (SEQ ID NO. 19) amino acid sequence, and CDR3 having an NREDFDY (SEQ ID NO. 20) amino acid sequence, and an H-chain constant region of a non-rat mammalian antibody. Also provided is a pharmaceutical composition containing the anti-LAG-3 antibody as an active ingredient. Also provided is a method of producing the anti-LAG-3 antibody.
