A modified amadoriase exhibiting a lower ratio of oxidase activity to dehydrogenase activity (OX/DH) compared to an amadoriase before modification selected from the group consisting of the following: (i) an amadoriase comprising an amino acid sequence having 85% or higher sequence identity with the amino acid sequence of SEQ ID NO: 3, SEQ ID NO: 6, SEQ ID NO: 9, SEQ ID NO: 10, SEQ ID NO: 11, SEQ ID NO: 44, SEQ ID NO: 53, or SEQ ID NO: 67 over the full length, said amadoriase comprising, when aligned with the amino acid sequence as shown in SEQ ID NO: 1, a substitution of the amino acid at the position corresponding to position 267 of the amino acid sequence as shown in SEQ ID NO: 1 and having dehydrogenase activity; (ii) an amadoriase comprising an amino acid sequence having 90% or higher sequence identity with the amino acid sequence of SEQ ID NO: 3, SEQ ID NO: 6, SEQ ID NO: 9, SEQ ID NO: 10, SEQ ID NO: 11, SEQ ID NO: 44, SEQ ID NO: 53, or SEQ ID NO: 67 over the full length, said amadoriase comprising, when aligned with the amino acid sequence of SEQ ID NO: 1, a substitution of the amino acid at the position corresponding to position 267 of the amino acid sequence of SEQ ID NO: 1 and further comprising substitution, deletion, or addition of one to ten amino acids at positions other than those corresponding to position 267 of the amino acid sequence as shown in SEQ ID NO: 1 and having dehydrogenase activity; or (iii) an amadoriase comprising, when aligned with the amino acid sequence of SEQ ID NO: 1, a substitution of the amino acid at the position corresponding to position 267 of the amino acid sequence of SEQ ID NO: 1, said amadoriase comprising an amino acid sequence having 85% or higher sequence identity with the amino acid sequence as shown in SEQ ID NO: 3, SEQ ID NO: 6, SEQ ID NO: 9, SEQ ID NO: 10, SEQ ID NO: 11, SEQ ID NO: 44, SEQ ID NO: 53, or SEQ ID NO: 67 over the full length and 90% or higher sequence identity between the amino acid sequence of a homologous region consisting of amino acids at positions 10 to 32, 36 to 41, 49 to 52, 54 to 58, 63 to 65, 73 to 75, 84 to 86, 88 to 90, 120 to 122, 145 to 150, 156 to 162, 164 to 170, 180 to 182, 202 to 205, 207 to 211, 214 to 224, 227 to 230, 236 to 241, 243 to 248, 258 to 261, 266 to 268, 270 to 273, 275 to 287, 295 to 297, 306 to 308, 310 to 316, 324 to 329, 332 to 334, 341 to 344, 346 to 355, 357 to 363, 370 to 383, 385 to 387, 389 to 394, 405 to 410, and 423 to 431 of the amino acid sequence as shown in SEQ ID NO: 1 and the amino acid sequence of the homologous region consisting of corresponding positions of the amadoriase and having dehydrogenase activity. (i) an amadoriase comprising an amino acid sequence having 85% or higher sequence identity with the amino acid sequence of SEQ ID NO: 3, SEQ ID NO: 6, SEQ ID NO: 9, SEQ ID NO: 10, SEQ ID NO: 11, SEQ ID NO: 44, SEQ ID NO: 53, or SEQ ID NO: 67 over the full length, said amadoriase comprising, when aligned with the amino acid sequence as shown in SEQ ID NO: 1, a substitution of the amino acid at the position corresponding to position 267 of the amino acid sequence as shown in SEQ ID NO: 1 and having dehydrogenase activity; (ii) an amadoriase comprising an amino acid sequence having 90% or higher sequence identity with the amino acid sequence of SEQ ID NO: 3, SEQ ID NO: 6, SEQ ID NO: 9, SEQ ID NO: 10, SEQ ID NO: 11, SEQ ID NO: 44, SEQ ID NO: 53, or SEQ ID NO: 67 over the full length, said amadoriase comprising, when aligned with the amino acid sequence of SEQ ID NO: 1, a substitution of the amino acid at the position corresponding to position 267 of the amino acid sequence of SEQ ID NO: 1 and further comprising substitution, deletion, or addition of one to ten amino acids at positions other than those corresponding to position 267 of the amino acid sequence as shown in SEQ ID NO: 1 and having dehydrogenase activity; or (iii) an amadoriase comprising, when aligned with the amino acid sequence of SEQ ID NO: 1, a substitution of the amino acid at the position corresponding to position 267 of the amino acid sequence of SEQ ID NO: 1, said amadoriase comprising an amino acid sequence having 85% or higher sequence identity with the amino acid sequence as shown in SEQ ID NO: 3, SEQ ID NO: 6, SEQ ID NO: 9, SEQ ID NO: 10, SEQ ID NO: 11, SEQ ID NO: 44, SEQ ID NO: 53, or SEQ ID NO: 67 over the full length and 90% or higher sequence identity between the amino acid sequence of a homologous region consisting of amino acids at positions 10 to 32, 36 to 41, 49 to 52, 54 to 58, 63 to 65, 73 to 75, 84 to 86, 88 to 90, 120 to 122, 145 to 150, 156 to 162, 164 to 170, 180 to 182, 202 to 205, 207 to 211, 214 to 224, 227 to 230, 236 to 241, 243 to 248, 258 to 261, 266 to 268, 270 to 273, 275 to 287, 295 to 297, 306 to 308, 310 to 316, 324 to 329, 332 to 334, 341 to 344, 346 to 355, 357 to 363, 370 to 383, 385 to 387, 389 to 394, 405 to 410, and 423 to 431 of the amino acid sequence as shown in SEQ ID NO: 1 and the amino acid sequence of the homologous region consisting of corresponding positions of the amadoriase and having dehydrogenase activity.