Electrocardiogram data and acceleration data obtained by a portable electrocardiograph of each patient are transmitted to a radio base station, and transmitted from the radio base station to a hospital computer via a public network, a line L, and a TA. Electrocardiograms and accelerations of a plurality of patients are displayed on the screen of the hospital computer based on the electrocardiogram data and acceleration data in real time. In the portable electrocardiograph, a communication device and an interface unit for communication are separated from other components by a ground plane, and an electrocardiogram measurement device is separated from the other components by a ground plane. Two of the ground planes are provided between the communication device and the interface unit for communication and the electrocardiogram measurement device.