1. An electrical impedance measuring apparatus comprising: a plurality of electrodes which are adapted to be adhered to a periphery of a chest of a living body; a potential measurer which is configured to perform a process of applying a current to any ones of the electrodes, and measuring potentials by means of other electrodes, on all of the electrodes while changing the electrodes to which the current is to be applied; an impedance acquirer which, based on the applied current and the potentials obtained by the potential measurer, is configured to obtain information related to an impedance of each of meshes, a chest section divided into the meshes; and an average value calculator which is configured to obtain a whole-region average value of impedances of all meshes of the chest section, and which is configured to obtain an ROI average value of impedances of meshes contained in each of ROIs, a whole region of the chest section segmented into the ROIs.