An auxin-producing bacteria (3YN11-02) was isolated from waste mushroom bed from Agaricus bisporus of Chungnam Buyeo-Gun area. The strain 3YN11-02 was identified as a novel species belongs to Rahnella aquatica by a chemotaxanomic and phylogenetic nalysis. The isolate was confirmed to produce indole-3-acetic acid (IAA) which is one of auxin hormone by TLC and HPLC analysis. When the concentration of IAA was assessed by performing HPLC quantity analysis, the maximal $290mg;L^{-1}$ of IAA detected in ether fraction extracted from the culture filtrate which was cultured in R2A broth containing 0.1% tryptophan for 24 h at $35^{circ}C$. The molecular weight of the main peak obtained by LC-mass analysis was correspondent well to 175, that of IAA. To investigate the growth promoting effect of crop, when the culture broth of R. aquatica 3YN11-02 was infected onto water culture and seed pot of mung bean, the adventitious root induction and root growth of mung bean were 2.0 times higher than control.