Provided is a drive assistance device for assisting driving of a vehicle by using an automatic driving function. Assuming various conditions of the driver, a plurality of notification timings to notify of switching from an automatic driving mode to a manual driving mode is set. Notifying a driver who is drowsing at a notification timing of long premature time allows the driver to have sufficient time margin to be ready for manual driving and to shift to driving action more safely. A driver who is reading a book or operating a smartphone is expected to be able to shift to driving action immediately after a notification, and thus it is sufficient to notify at a notification timing of short premature time, which can reduce inconvenience for the driver.