Abstract: A measuring device provided with a memory unit for storing correction data, wherein the memory unit is controlled by a control circuit; the correction data is transmitted to a main memory through an input-output device; a transducer measures living body data, and converts the measured data into an electric signal; a digital signal converted from the electric signal by an analog-digital converter is delivered to a central processing unit as measured data; the transducer, memory unit and control circuit jointly constitute a measurement-correcting module, which is detachably attached to the input-output device; the central processing unit corrects the measured data by the correction data stored in the main memory, and converts the corrected measured data into a display signal; and a display device indicates the measured data in accordance with the display signal received.