Rhizopogon roseolus (Corda) Th. M. Fr. (=R. rubescens Tul. & Tul.), known as “shoro” in Japan, is a hypogeous basidiomycete that is an important ectomycorrhizal symbiont of Pinaceae. In order to cultivate this edible ectomycorrhizal mushroom, several researches have tried to promote mycorrhization of this mushroom on host Pinus thunbergii roots: Pine seedlings were inoculated with mycelium in vitro, or with crushed fruiting bodies in nature. However, successful cultivation of this mushroom has not been fully refined. We have developed the useful mycelial inoculum that enable to produced abundant ectomycorrhizas and then to form fruiting body under greenhouse nursery conditions. We selected the superior strain that rapidly colonized and produced a lot of ectomycorrhizas in root of P. thunbergii． The mycelial inoculum was composed of mineral solution and homogenate of mycelium that had been cultured in liquid medium. Addition of surfactant in the mycelial inoculum resulted in stimulation of mycorrhzal formations in host roots. When the mycelial inoculum containng surfactant were introduced to the mother plant system in which the colonized seedling had been planted into in the nursery, stimulatally effects were observed on not only mycorrhzation of the seedlings but also fruiting body formation. Genotype analysis using microsatellite markers for R. roseolus showed that fruiting bodies produced in the nursery were originated from the inoculated strain. These results suggest that the mycelial inoculum containg surfactant could be the model of mycelial spawn for “shoro”.