A portable electrocardiograph serving as a biological information measurement device includes a negative electrode and a positive electrode brought in contact with a living body, a processing circuit processing a biological electric signal detected by these measurement electrodes, an output terminal for supplying the obtained biological information to an external terminal unit, a first contact point electrically connected to the negative electrode and the positive electrode, a second contact point electrically connected to the processing circuit, a cover covering the output terminal in a cover-closed state and exposing the output terminal in a cover-opened state. The portable electrocardiograph is structured such that the first contact point is electrically connected to the second contact point when the cover is closed and the first contact point is electrically disconnected from the second contact point when the cover is opened.