A control unit obtains, from a memory unit, data of a plurality of pre-meal blood sugar levels that are blood sugar levels measured before meals and data of a plurality of post-meal blood sugar levels that are blood sugar levels measured after meals, calculates a pre-meal average value that is an average value of the plurality of pre-meal blood sugar levels, calculates a post-meal average value that is an average value of the plurality of post-meal blood sugar levels, calculates an average blood sugar level that is an average of the pre-meal average value and the post-meal average value, calculates an estimated HbA1c value using the average blood sugar level, and displays the calculated estimated HbA1c value in a display unit.
