Isoquercitrin (IQ), quercetin monoglycoside, is classified as a polyphenol, and a minute quantity of IQ is known to be present in several plants. Recently, it was reported that IQ can be prepared by the partial enzymatic hydrolysis of quercetin diglycoside (rutin, RU). In this paper, the effects of enzyme types, enzyme amounts, and substrate concentrations on the reactivity were investigated using a series of $Pecinex^{TM}$ multi-enzymes. The reaction, when a 8 ml of Ultra Clear to 1 g of RU was applied with the substrate concentration of 1% at $50^{circ}C$, was found to be optimum, based on the reaction rate and the selectivity to IQ.