There is provided a mobile blood-sugar level measuring system 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 blood-sugar level measuring system is formed by using a blood-sugar level processing device including a data-arithmetic-processing unit for arithmetically processing the measurement-data, an external data importing unit for entering and accumulating external data on blood-sugar level, a display device for displaying the result of the arithmetic-processing, and a display device control unit for controlling the display device, in combination with a conventional, mobile blood-sugar level monitoring device.