Departure time choice of trips has been an essential topic in the research of traffic congestion. This study targets at the departure time choice of tourism purpose trip with a particular focus on the homeward trips after sightseeing. It presented an analysis of data collected by an experimental route search mobile application developed by the authors that provides travel times of 'Depart time' and predicted travel time of 'Depart later'. The influencing factors that impact on the departure time choice, such as personal characteristics and route search attributes, are examined. The research results found that travelers are more likely to choose 'Depart later' when the travel time of 'Depart later' is over 10 minutes shorter than that of 'Depart now'.