An impeller is employed for a fuel pump and boosts a pressure of fuel by rotating the fuel in a pump passage formed in the fuel pump in a rotational direction of the impeller. The impeller includes a plurality of vane grooves formed adjacent to each other in the rotational direction of the impeller and a plurality of vanes formed adjacent to each other in the rotational direction. Each one of the plurality of vanes divides one of adjacent two of the plurality of vane grooves from the other. A difference between a maximal value and a minimum value of an adjacent vane angle is set in a range of 2.5° to 4°. A fuel pump includes a motor unit, the impeller, and a casing member. The impeller is rotated by rotation driving force of the motor unit. The casing member rotatably receives the impeller and defines the pump passage.