A casing of a housing of a fuel pump has a bearing surface that rotatably supports an inner gear in an axial direction from a motor side while a plain bearing extends through the bearing surface. The plain bearing includes: an inner-peripheral-side step that is stepped by increasing an inner diameter of the plain bearing on a counter-motor side of the inner-peripheral-side step in the axial direction; and an outer-peripheral-side step that is stepped by increasing an outer diameter of the plain bearing on the motor side of the outer-peripheral-side step at a position that is on the motor side of the bearing surface in the axial direction.