Effect of isoliquiritigenin isolated from the heartwood of Dalbergia odorifera T. Chen (Leguminosae) on mushroom tyrosinase activity was investigated in vitro using L-tyrosine and L-3, 4-dihydroxyphenylalanine (L-DOPA) as the substrates. When L-tyrosine was used as a substrate, both isoliquiritigenin and kojic acid, a positive control, inhibited tyrosinase activity in a concentration-dependent manner. IC$_{50}$ values of isoliquiritigenin and kojic acid were 61.4 and 52.2 ${muM}$, respectively. However, isoliquiritigenin showed week inhibitory effect on the oxidation of L-DOPA by tyrosinase with inhibition ratio of 9.1 ${pm}$ 7.1% at 100 ${muM}$. It is also suggested that 3-unsubstituted and 4-hydroxyl phenyl group in isoliquiritigenin plays an important role on the inhibition of tyrosinase activity when L-tyrosine was used as a substrate. Analysis of Lineweaver-Burk plot showed that isoliquiritigenin acts as a competitive inhibitor in case of L-tyrosine as a substrate.