Behavioral synchronization is shown not only between intra-species but also between inter-species. Previous studies reported that behavioral synchronization occurs between dogs and their owners by affiliative bonds and dogs' social skills for communicating with humans acquired by domestication. Horses also have such bonds and skills like dogs, however, there have been few empirical studies of behavioral synchronization between horses and humans. Therefore, we investigated whether the gait synchronization occurs between the horse and his/her familiar human participant while they were walking together by using angular statistics and how horses and umans interacted by analyzing entrainment. Only when human gait rhythm was controlled to be constant, gait synchronization between horse and human participants was found, though entrainment occurred only in humans. When horses and humans were walking in a more natural and uncontrolled situation, entrainment occurred in both horses and humans, though their walk adjustment did not reach synchronization. These results suggest that gait synchronization occurs between horses and humans and walk adjustment from humans is involved in such synchronization.