Abstract: Production of air containing minus alkali ion. As shown in FIG. 2, there is shown an electric stone fine powder 20 having the grain size of 0.3 to 3 microns on the average, an electric stone carrier having the electric stone fine powder 20 uniformly mixed therewith, which is in the form of clothes having a volume intrinsic DC electric resistance of 10.sup.7 to 10.sup.10 .OMEGA..cm. This constitutes a vent contact reaction portion 2 as shown in FIG. 3. This portion 2 is located above an air intake 1a at the lower part of a box 1 and extended over the whole internal surface of the box 1. Ventilation means 3 formed from an electric fan causes the electric stone carrier 30 to subject to direct forced ventilation into contact with air, and minus alkali ion is prepared from water molecules which are moisture in air. The air containing the minus alkali ion is delivered from an air port 1b provided at the upper part of the box 1 to an installation spot.