An apparatus for ensuring a fail-safe function of an autonomous traveling system may include: a dead reckoning (DR) information input unit configured to receive plural pieces of sensing information outputted from a plurality of sensors mounted in a vehicle as DR information; an identification value calculation unit configured to calculate an identification value for determining whether the respective pieces of sensing information inputted through the DR information input unit are fails; and a fail determination unit configured to determine whether the plural pieces of sensing information inputted through the DR information input unit are fails, using the identification value calculated through the identification value calculation unit, wherein the identification value calculation unit is configured to calculate the identification value for determining whether the pieces of sensing information are fails, using a rule-based method.