It is intended to provide a preventive agent for ascites containing coenzyme Q which can sufficiently exert an effect on preventing ascites even when administering in a small dose and within a short period of time, and the preventive agent for ascites which can be effectively administered to poultry using a simple method. Namely, preventive agent for ascites in poultry containing coenzyme Q and a surfactant, wherein the content of the surfactant is in a range of between 0.5 and 80 parts by weight with respect to a total amount of the preventive agent for ascites.