An internal temperature sensor for measuring internal temperature of a case of the blood glucose meter is arranged inside the case of the blood glucose meter, and an external temperature sensor configured by components with low heat capacity and adapted for measuring external temperature is arranged at a position separated from the central portion of the case of the blood glucose meter. Further, a microcomputer of the blood glucose meter includes the following processing: judging whether or not the temperature fluctuation falls within the acceptable range based on the difference between the respective temperatures and, if the temperature fluctuation exceeds the acceptable range, temporarily stopping the processing until the temperature fluctuation falls within the acceptable range when in the case where the blood glucose measurement has not yet been performed, or stopping the blood glucose measurement processing when in the case where the blood glucose measurement is being performed.
