[Problem] To provide a process suitable for mass-producing of iso-liquiritigenin.[Solution] A process for preparing iso-liquiritigenin, which comprises steps of coupling a 4-alkoxycinnamic acid represented by formula (I) with a 1,3-alkoxybenzene represented by formula (II) through the Friedel-Crafts reaction (A) to synthesize a tri-alkoxy-iso-liquiritigenin represented by formula (III), to crystallize out the reaction product, and eliminating the protecting groups therefrom to obtain iso-liquiritigenin, represented by formula (IV). The iso-liquiritigenin (IV), is administered as a precursor for liquiritigenin represented by formula (V) to the body, thereby obtaining in vivo a pharmacological effect of the (−) isomer of liquiritigenin.