A gram-negative bacterium was isolated from spent substrate of and showed marked antagonistic activity against . The bacterium was identified as by based on the cultural, biochemical and physiological characteristics, and 16S rRNA gene sequence. The isolated bacterium was saprophytic but not parasitic nor pathogenic to cultivation mushroom. The isolated bacterium for cell was not sufficient for inhibition . Control efficacy of HC5 to brown blotch of was 73, 78, and 71% on , , and , respectively. In the future, the suppressive bacterium may be useful for development of a biocontrol system.