The white-spotted chafer, Protaetia brevitarsis (Coleoptera: Scarabaeidae) was recently listed as a temporal food ingredient by the Korean Ministry of Food and Drug Safety. Traditionally, this beetle has been regarded as a medicine for suppressing live cancer and preventing liver-related disease. Based on these facts, this beetle has been focused as a economically important insects in Korea. Therefore, this beetle is commercially reared and distributed in Korea. As the economic importance is growing, we have investigated to enhance insect rearing conditions for better commercial value. In this study, we compared two food supplements, clay and charcoal, on the larval weight gain for second instar larvae of P. brevitarsis. Clay and charcoal are generally known as a good adsorbent for heavy metals and bio-waste. However, clay and charcoal is not a conventional feed supplements, so its effects were not investigated for insect rearing. The second instar P. brevitarsis larvae were fed fermented sawdust with seven different combinations of cla and/or charcoal, and measured body weight for 17 weeks until pupated. Addition of clay at 2.5 % w/w of the fermented sawdust diet had no negative effect on larval weight gain, and thus may improve the quality of P. brevitarsis as a commercial food.