Euphorbia hirta L. is one of the potential sources for functional food material due to its sufficient biological activity coming from its active flavonoid. Quantitative analysis of its active substances using an adequate method and determining the plant part which possesses the highest yield are essential. However, there was no study reported such that information. Therefore, this study was aimed to analyze flavonoid content (quercitrin and myricitrin) of the three parts (leaf, flower, and stem) of E. hirta in order to determine the part with the highest productivity for production of bioflavonoid-rich extract. A precise and accurate HPLC quantitative analysis was performed to quantify the content of quercitrin and myricitrin in the ethanol extracts of leaves, flowers, and stems of E. hirta. The HPLC analysis showed that quercitrin and myricitrin was the most dominant flavonoid in the leaf, flower, and stem of E. hirta. The leaves exhibited the highest yield of quercitrin and myricitrin (27.55 mg/g and 8.43 mg/g, respectively). It was more than two times of the content of those substances in the flowers and stems. Thus, it can be determined that leaf was the prominent part of E. hirta, especially for the production of bioflavonoid-rich extract which can be used as a functional food active substance.