The present invention is about a method of afforesting infertile soil using the mycorrhizal fungus Pisolithus tinctorius as a microbial fertilizer and adding soil improving compounds. The method is capable of afforesting infertile soil by introducing Pisolithus tinctorius to help planted plants to grow well, thereby making forest trees or landscape trees healthier and promoting growth. Consequently, it is possible to improve infertile soil and to increase the usability of soil. The present invention may contribute to increasing the forest productivity, reduction of environmental pollution and restoration of damaged forest ecosystem.