To provide a feed pump 3 improving pump performance by reducing side clearances in an axial direction at both sides of a pump element PE.

The feed pump 3 as this fuel supply device is constructed in such a manner that an outer rotor 22 and an inner rotor 23 constructing the pump element PE have through holes 22a, 23a formed on a tooth tip part of the outer rotor 22 and a tooth tip part of the inner rotor 23 respectively. Consequently, since side clearances provided in both axial sides of the rotors 22, 23 are communicated with each other, pressure in a thrust direction can be equalized in the both sides of the both rotors 22, 23 in the axial direction. Consequently, the both rotors 22, 23 do not have metal-to-metal contact with a pump cover 19 and a pump plate 20 and can be floated, troubles such as abnormal wear and seizure can be suppressed even if side clearance between the pump cover 19 and the pump element PE is set small.