This invention provides an amadoriase that can react with a wide variety of glycated peptides generated upon hydrolysis of the β chain of hemoglobin A1c (HbA1c) to generate hydrogen peroxide, a method for measurement of HbA1c using such amadoriase, and a reagent kit for measurement of HbA1c using such amadoriase. Provided is an amadoriase obtained by substitution of one or more amino acids at positions corresponding to amino acids selected from the group consisting of amino acids 62, 63, 102, 106, 110, 113, and 355 in the amino acid sequence of the amadoriase derived from the genus Coniochaeta or the like which amadoriase is capable of oxidizing a wide variety of glycated peptides to generate hydrogen peroxide. Further provided is a method for measurement of HbA1c comprising using such amadoriase as well as a reagent kit for measurement of HbA1c comprising such amadoriase. This invention can provide a method for measurement of HbA1c that enables quantification of HbA1c to be performed rapidly, simply, and accurately with the use of a small amount of a protease and a kit used for such measurement. This invention can also provide a method for measurement of HbA1c that enables quantification of HbA1c to be performed rapidly, simply, and accurately, with high sensitivity with the use of a small amount of a protease and a kit used for such measurement.