To provide a fuel supply device capable of securing a stable transport of the fuel from a sub-tank of a saddle type fuel tank arrangement to its main tank and suppressing the fuel temperature supplied to a delivery passage.

The fuel supply device is equipped with a first chamber 6 surrounding the suction hole of the delivery passage 12 and the discharge hole of a saddle transporting passage 22, a second chamber 7 surrounding the discharge hole of a return passage 16 and the suction hole of the saddle transporting passage 22, a transport pump 23 installed in the saddle transporting passage 22, and a suction passage 16 provided in the sub-tank 3 and connected with the saddle transporting passage 22. The fuel having good fluidity heated by the return fuel flows through the saddle transporting passage 22, which secures a stable transport of the fuel from the sub-tank 3 to the main tank 2 via the suction passage 16 and the saddle transporting passage 22. Even if the operation is made with high load and with the outer air at high temperature, it is possible to suppress the fuel temperature supplied to the delivery passage 12 to the allowable level or below it.