A fuel supply apparatus (30) for a general purpose engine (10) includes a carburetor (42) provided in an air intake line (31) extending from an air cleaner (41) to the general purpose engine (10), a pressure reduction connection channel (81) connected to a float chamber (63) of the carburetor (42) and the air cleaner (41), a control valve (82) provided in the pressure reduction connection channel (81), a pressure reduction pump (83) provided in the pressure reduction connection channel (81) and sucking the float chamber (63) to reduce the pressure therein, an air fuel ratio sensor (84) detecting the air fuel ratio of an exhaust gas discharged from the general purpose engine (10), and a control unit (85) controlling the opening degree of the control valve (82) based on a detection signal of the air fuel ratio sensor (84).