An Fc-binding protein, comprising the amino acid residues from position 33 to position 208 of the amino acid sequence according to SEQ ID NO: 37, wherein the Fc-binding protein has an improved heat stability, and wherein at least any one of the amino acid substitution of the following to is introduced in the amino acid residues from position 33 to position 208: valine at position 133 of SEQ ID NO: 37 is substituted with glutamic acid, phenylalanine at position 45 of SEQ ID NO: 37 is substituted with isoleucine and valine at position 133 of SEQ ID NO: 37 is substituted with glutamic acid, phenylalanine at position 187 of SEQ ID NO: 37 is substituted with serine, glutamine at position 64 of SEQ ID NO: 37 is substituted with arginine, aspartic acid at position 98 of SEQ ID NO: 37 is substituted with glutamic acid, glutamine at position 128 of SEQ ID NO: 37 is substituted with leucine, lysine at position 135 of SEQ ID NO: 37 is substituted with asparagine, leucine at position 158 of SEQ ID NO: 37 is substituted with glutamine, asparagine at position 196 of SEQ ID NO: 37 is substituted with serine, isoleucine at position 204 of SEQ ID NO: 37 is substituted with valine, tyrosine at position 67 of SEQ ID NO: 37 is substituted with serine and glutamine at position 106 of SEQ ID NO: 37 is substituted with arginine, phenylalanine at position 77 of SEQ ID NO: 37 is substituted with tyrosine, lysine at position 135 of SEQ ID NO: 37 is substituted with glutamic acid and leucine at position 191 of SEQ ID NO: 37 is substituted with arginine, and phenylalanine at position 45 of SEQ ID NO: 37 is substituted with leucine, glutamic acid at position 55 of SEQ ID NO: 37 is substituted with glycine, aspartic acid at position 93 of SEQ ID NO: 37 is substituted with glycine and threonine at position 156 of SEQ ID NO: 37 is substituted with isoleucine. valine at position 133 of SEQ ID NO: 37 is substituted with glutamic acid, phenylalanine at position 45 of SEQ ID NO: 37 is substituted with isoleucine and valine at position 133 of SEQ ID NO: 37 is substituted with glutamic acid, phenylalanine at position 187 of SEQ ID NO: 37 is substituted with serine, glutamine at position 64 of SEQ ID NO: 37 is substituted with arginine, aspartic acid at position 98 of SEQ ID NO: 37 is substituted with glutamic acid, glutamine at position 128 of SEQ ID NO: 37 is substituted with leucine, lysine at position 135 of SEQ ID NO: 37 is substituted with asparagine, leucine at position 158 of SEQ ID NO: 37 is substituted with glutamine, asparagine at position 196 of SEQ ID NO: 37 is substituted with serine, isoleucine at position 204 of SEQ ID NO: 37 is substituted with valine, tyrosine at position 67 of SEQ ID NO: 37 is substituted with serine and glutamine at position 106 of SEQ ID NO: 37 is substituted with arginine, phenylalanine at position 77 of SEQ ID NO: 37 is substituted with tyrosine, lysine at position 135 of SEQ ID NO: 37 is substituted with glutamic acid and leucine at position 191 of SEQ ID NO: 37 is substituted with arginine, and phenylalanine at position 45 of SEQ ID NO: 37 is substituted with leucine, glutamic acid at position 55 of SEQ ID NO: 37 is substituted with glycine, aspartic acid at position 93 of SEQ ID NO: 37 is substituted with glycine and threonine at position 156 of SEQ ID NO: 37 is substituted with isoleucine.