A guide plate mounting structure of a fuel pump, the guide plate mounting structure may include a fuel pump having a housing, a driving shaft protrudedly formed from the housing to the outside of the fuel pump, a block mounted onto an outer peripheral surface of the housing of the fuel pump, a guide plate having a first through hole formed at a center thereof and being positioned at an end of the block, and a fuel pump gear having a second through hole formed at a center thereof and being mounted to the driving shaft of the fuel pump through the second through hole, and a rim formed on an end surface of the fuel pump gear so as to be inserted into a first end surface of the guide plate.