A travel lane marking probability calculating unit calculates a travel lane marking probability of each of travel lane marking candidates based on a calculation condition. A travel lane marking recognizing unit recognizes, as a travel lane marking, a travel lane marking candidate having a travel lane marking probability that is a threshold value or higher, among the travel lane marking candidates. A lane change detecting unit detects that an own vehicle is in the midst of a lane change. When the own vehicle is in the midst of a lane change, a condition changing unit changes the calculation condition to allow the travel lane marking probability to be more easily increased compared to when the own vehicle is not in the midst of a lane change, or changes the threshold value to be lower than that when the own vehicle is not in the midst of a lane change.