A pump body of a high-pressure pump includes a pressure chamber formed in a deep portion of a cylinder. The pump body closes the pressure chamber on a side opposite to a plunger. The plunger reciprocates within the cylinder to vary a volume of the pressure chamber. The large-diameter portion provided at an end of the plunger on a side protruding to the pressure chamber has an outside diameter larger than an inside diameter of the cylinder and smaller than an inside diameter of the pressure chamber. In this case, the large-diameter portion is engaged with a step portion between the cylinder and the pressure chamber in a state before attachment of the high-pressure pump to an internal combustion engine. Accordingly, separation of the plunger from the cylinder is avoidable.