A plurality of electron-emitting devices carried on a device substrate are arranged vis-a-vis an acceleration electrode carried on a face plate. The device substrate and the face plate, together with side walls disposed therebetween, constitute an envelope the inner space of which is kept under vacuum. A number of spacers are also disposed between the device substrate and the face plate within the inner space. The electric potential Va applied to the acceleration electrode, the distance l between the electron-emitting devices and the corresponding respective spacers, and the distance d between the electron-emitting devices and the acceleration electrode satisfy the relationship, Va·l2/d2>|&Dgr;Vsat|/(2·&agr;·&bgr;), where &agr; and &bgr; are constants determined from several factors and &Dgr;Vsat is the potential deviation of the spacer surface under charged conditions from that under uncharged conditions.