Abstract: A fuel supplying device is provided with a supplemental fuel chamber such that there is no delay in the supply of fuel during high-speed operation. The fuel supplying device comprises: an outlet pipe in communication with a fuel injecting nozzle equipped in an intake manifold of an engine or an air intake passage of a carburetor; a pressing member configured to undergo reciprocating motion synchronized with the rotational period of an engine; a fuel chamber configure to supply fuel to an intake manifold of the engine from the fuel injecting nozzle through cooperation of the reciprocating motion of the pressing member, wherein the inlet check valve and the outlet check valve are configured to open and close alternatingly; and a fuel reservoir having a prescribed volume is connected and disposed upstream of the inlet check valve in the inlet pipe.