The purpose of the present invention is to actively utilize a function of charcoal or bamboo charcoal to produce a space in which negative charges are predominant irrespective of the configuration of the equipment or device for use in a step for the production or processing of a food or foodstuff.A coating material (2a) containing graphitized charcoal or bamboo charcoal as a major component is applied to ceramic sheets (21) in such an amount as to result in a resistivity of 3±1 kilo-ohms (kΩ), thereby forming planar electrodes (2). This planar electrodes (2) are attached to the wall surface part (11), ceiling part (12), and chamber (12a) of a storage room (1a, 1b) so that the surfaces of the planar electrodes (2) to which the coating material (2a) was not applied come into contact therewith. A direct-current negative voltage of -70 to -100 volts is applied to the planar electrodes (2) (coating material (2a)) from a voltage application member (3) through an electric wire to excite the carbon contained in the attached planar electrodes (2), and a space in which negative charges are predominant is produced inside the housing room (1a, 1b) by the action of the electrons (e) present in the planar electrodes (2) or released therefrom.
