A bacterial strain producing a novel endo-inulinase, hydrolysing inulin into oligosaccharides was isolated from soil and identified as Arthrobacter sp. S37 The enzyme production was induced by inulin and jerusalem artichoke extract. The maximum enzyme production was obtained with medium containing 1.5% jerusalem artichoke extract, 1.0% yeast extract, $0.5%;NaNO_3,;0.05%;MgSO_4{cdot}7H_2O,;0.05%;KCl,;0.0016%;FeCl_3{cdot}6H_2O;and;0.05%;KH_2PO_4$. The optimum temperature and pH for the enzyme production were $30^{circ}C$ and 8.0, respectively. Under the optimum condition, the enzyme activity in the culture broth reached at maximum, 10.8 units/ml after cultivation for 24 hours.