A microbe propagation preventing apparatus is provided to prevent an ion from decreasing at a time of decomposing ozone generated by gaseous discharge or ionization so as to sufficiently generate air ion, and to sufficiently prevent propagation of microbes adhering to an object by using the air ion without secondary pollution. Further, in the apparatus, a gas containing the ion is supplied into water so as to prevent the microbe propagation in the water. In the apparatus, an ozone decomposing chamber is mounted to be electrically insulated from an air duct. An electrode to remove a positive ion is mounted to obtain only a negative ion, and extend a lifetime of the obtained ion. An ion supplying portion is mounted to supply an ionized gas into a space housing the object in which microbes can be propagated, and return the ionized gas to an ionization chamber. Further, a diffusing apparatus is provided to transform the ionic gas into bubbles so as to feed the bubbles into the water in the water reservoir.