An automatic driving system includes a driver monitor, a driver state determining unit, a first automatic driving controller, and a second automatic driving controller. The first automatic driving controller controls a first automatic driving mode for causing a vehicle to travel by automatic driving under a preset first traveling environment regardless of whether a driver is in a forward monitoring state. The second automatic driving controller controls a second automatic driving mode for causing the vehicle to travel by the automatic driving in a situation where the driver state determining unit determines, based on a driver state detected by the driver monitor, that the driver is in the forward monitoring state, and the vehicle is under a second traveling environment which is more complicated than the first traveling environment.