There is provided a mobile blood-sugar level monitoring device enabling a diabetic patient to accurately and easily perform management of blood-sugar level measurement timing, management of changes in blood-sugar level, and further prediction of a future blood-sugar level. The mobile blood-sugar level monitoring device having the function to measure the blood-sugar level and manage the obtained measurement data is provided with a data arithmetic-processing unit for arithmetically processing the measurement data by a predetermined method, displaying the result of the arithmetic process, and notifying measurement-timing for the blood-sugar level and a predicted blood-sugar level to the diabetic patient.