Since cannibalism is often considered as rare and accidental phenomenon, it has been ignored in ecological researches. Cannibalisms of predators can affect prey community and its ecosystem function such as material flux by modifying the predators’ top-down impacts. We conducted an outdoor experiment using pond community, in which cannibalism of salamander larvae (Hynobius retardatus) was controlled to explore its ecological consequences. Compared to non-cannibalistic situation, in the cannibalistic situation, small-sized prey (aquatic insect larvae) were exposed to lower predation pressure, but large-sized prey (Rana pirica frog tadpoles) were exposed to higher predation pressure from the salamanders. As a result, more aquatic insects but fewer frogs metamorphosed in the cannibalistic situation. Hence, dynamics of energy flow from the pond to terrestrial system was regulated by cannibalisms of the salamanders through the contrasting effects of cannibalisms on their top-down impacts on the two prey groups. Cannibalism of this salamander species may play prominent roles in dynamics of pond community and ecosystem functioning.