The extraction and enzymatic treatment conditions of ginseng leaves, stems and roots for the production of fermented ginseng were optimized in order to enhance the extraction of oligosaccharide, which is a Lactobacillus growth-activating factor. Additionally, the effects of enzymatic hydrolysis on Lactobacillus fermentation characteristics and metabolites of ginsenoside were investigated. The ginseng leaves were found to be more suitable for the raw material of fermented ginseng products because ginseng leaves have higher carbohydrate and crude saponin content than ginseng roots. The optimized conditions were found as particle size of ginseng raw material below 0.15 mm, pH 5.0-5.5, reaction temperature of 55-60 ℃, Ceremix concentration of 1%, and reaction time of 2 h. It was shown that the polysaccharides of ginseng were hydrolysed to oligosaccharide by the enzymatic hydrolysis of ginseng leaves, stems and roots. The total oligosaccharide content increased by the enzyme treatment up to 2.2-fold, 5.3-fold and 2.3-fold in ginseng leaves, stems and roots, respectively, compared to control (no treatment). It was found that the enzymatic treatment promoted the Lactobacillus growth, resulting in more significant change in total oligosaccharide consumption and total acidity. The content of several metabolites of ginsenoside, such as Compound K, Rg1, Rh1 and Rg3, was selectively increased by combining the enzymatic treatment and Lactobacillus fermentation. Especially, in the case of enzyme treatment using ginseng leaves, Compound K formation was enhanced up to three-fold compared to control (no treatment). Moreover, in case of combined treatment of enzyme and fermentation, Compound K formation was significantly promoted up to ten-fold.