It is to provide a method for measuring glycated hemoglobin in a hemoglobin-containing sample, comprising: reacting glycated hemoglobin in the hemoglobin-containing sample with a proteolytic enzyme in the presence of at least one salt selected from the group consisting of a pyridinium salt, a phosphonium salt, an imidazolium salt, and an isoquinolinium salt; reacting the obtained reaction product with fructosyl peptide oxidase; and measuring the generated hydrogen peroxide. The present invention provides a method for accurately measuring glycated hemoglobin in a hemoglobin-containing sample.