The processing of Black Soldier Fly Larvae (BSFL) for high-quality animal feed protein is being promoted to transformation at the industry level in Thailand. This is due to the fact that the washing process of BSFL generates wastewater with high organic matter that must be treated. This research was interested in studying the potential of methane production from wastewater in the BSFL washing process that is fed by Inca meal and mixed with inoculum sludge from a swine biogas production system at different substrate and inoculum ratio of 3:1, 1:1 and 1:3 by gVS add. The system also controlled the temperature within the mesophilic condition at 35 ± 2°C. The result of this study shows that the optimum ratio which the most biochemical methane potential (BMP) was 1:1 on 45 days of fermentation period. This optimum ratio can also generate the cumulative methane gas production of 401.51 ± 24.42 NmL/gVS add with the highest methane content of 67.90%. The VS removal was 23.76% and the COD removal was 68.51%, which shows the BSFL washing process wastewater can be a substrate for biogas production and further expanded to the industry level.