To lead pressure at an appropriate position of a pump passage in a fuel pump to a back-pressure chamber of a pressure-regulation mechanism; and to improve pressure-regulation accuracy of the pressure-regulation mechanism without reducing the efficiency of the fuel pump.

The pressure-regulation mechanism 40 of a fuel supply device includes a the back-pressure chamber 423 connected with the pump passage of the fuel pump 30 by pressure transmitting means 13, 13a, and 13b, and the pressure-regulation chamber 422 connected with an out-of-tank fuel supply pipe 7. Fuel pressure in the pressure-regulation chamber 422 and fuel pressure in the out-of-tank fuel supply pipe 7 are adjusted in this structure in response to the fuel pressure of the back-pressure chamber 423. The pressure transmitting means 13, 13a, and 13b have a switching mechanism 130 formed to switch a plurality of pressure pulling-out sections so as to restrain pressure fluctuation in a plurality of pressure pulling-out sections arranged along the pump passage and the back-pressure chamber 423.