Mycorrhizal fungi that coexist with plants improve the absorption of inorganic nutrients into plants such as phosphate and are said to enhance heavy metal tolerance and disease resistance, as well. In this study, in order to investigate the effect of mycorrhizal fungi on heavy metal tolerance and disease resistance, I inoculated arbuscular mycorrhizal fungi (AMF) on Lotus japonicas cultured in a medium with an excess amount of zinc ion (Zn), and on Oryza sativa infected with Gibberella fujikuroi. As a result, the increased Zn concentration in the medium increased the infection rate of the AMF on the roots of L. japonicas. However, recovery of the growth rate of these plants was not observed. In O. sativa, inoculation of the AMF accelerated the root growth, whereas their effect on the control of G. fujikuroi could not be confirmed. It will be necessary to consider the culture conditions of O. sativa upon the inoculation of the AMF.