A fuel supply device includes a leaked fuel collection unit and a check valve. When fuel passes through a first seal member to leak out from a cam chamber into an inter-seal space, the leaked fuel collection unit sucks in this fuel to extract the fuel from the inter-seal space, then pressurizes and returns the fuel to a fuel tank. The check valve prevents the fuel from flowing in reverse from the fuel tank to the inter-seal space. Accordingly, regardless of the pressure in the fuel tank and the pressure in the inter-seal space, fuel that leaks into the inter-seal space may be actively returned to the fuel tank. Further, the check valve prevents pressure in the fuel tank from acting on seal members. Accordingly, fuel that leaks into the inter-seal space may be collected into the fuel tank.