A car undercover is provided. The car undercover includes: a cover main body installed on a lower end of a front frame carrier; a plurality of mount units formed by being spaced at a predetermined interval in a longitudinal direction on an end of the cover main body, in order to install the cover main body; and a reinforcement rib formed by being protruded in a vertically longitudinal direction on an internal side of the cover main body, in order to reinforce strength, wherein the reinforcement rib includes a stiffener formed by being protruded from the reinforcement rib in a shape opposite to a shape of the reinforcement rib. The car undercover may minimize damage of a pedestrian, by not being broken when colliding with the pedestrian. In addition, the car undercover may minimize damage of internal components, by being broken when colliding with a vehicle.