A diagnostic apparatus includes a stethoscope, an electrocardiac detector, a control unit, and an external unit. A sound detector is a chest piece to make contact with a patients skin, and includes a first detector to detect a relatively high frequency and a second detector to detect a relatively low frequency. The electrocardiac detector includes electrodes to detect potentials associated with heart beats, and is provided on each of the first and second detectors. The control unit converts electrocardiac signals detected by the electrocardiac detector into radio signals that are transmitted to the external unit. The external unit is a portable terminal apparatus, and includes a display unit formed by a liquid crystal panel on a front surface thereof, an operation part including operation buttons and ten-key, and patient selection buttons to select reading of data of patients.
