The present invention relates to a device for preventing an external substances from being inserted into the lower part of a foot pedal unit of a vehicle, and the device prevents external foreign substances from being inserted into the lower part of a vehicular foot pedal unit which includes a pedal arm and a pedal combined with an edge of said pedal arm, wherein the invention comprises a body which: is formed as a clastic member that is clastically transformed; is disposed between a lower side of said foot pedal unit and an indoor bottom surface of the vehicle; and is combined with said foot pedal unit and/or said indoor bottom surface of the vehicle, wherein said body is formed to prevent external foreign substance from being introduced to the lower side of said pedal arm and said pedal. According to the present invention, no external substances are introduced to a lower gap between the pedal arm and the pedal when the vehicle is running, thereby is preventing fatal traffic accidents.