<p>Background: In the field of physical education at junior high school, Budo (judo, kendo, sumo) became a compulsory subject in 2012. In recent years, the characteristics of injuries in judo classes at junior high school have been reported. However, the characteristics of injuries in judo classes at senior high school are not clear.</p><p>Objective: The purpose of this study was to clarify the characteristics of injuries in judo classes in senior high school.</p><p>Methods: Data were collected from the “Injury and accident mutual aid benefit system data”, provided by JAPAN SPORTS COUNCIL. As a method, the quantitative text analysis “KH Coder” was used to identify the factors causing injuries. The target was the data of the injury accidents in high school judo classes. The target year was set as the 2012 academic year in order to compare with junior high school students, and the latest data available at the start of this study was that of the 2016 academic year.</p><p>Results: The main results were as follows: In the 2012 academic year, there were many descriptions of injuries for Ukemi practice in all grade levels of girls and for both Ukemi practice and Katame-waza (grappling techniques) in 1st grade boys. In terms of injury location, many of the girls described the head and neck areas. In the 2016 academic year, more descriptions of Ukemi practice injuries were found in 2nd grade girls, and 1st grade boys. In terms of injury location, the head and neck regions were described more frequently by girls.</p><p>Conclusion: Injury accidents in judo classes at senior high schools were characterized by a large number of descriptions of Ukemi practice by 1st grade boys and all grade levels of girls, with girls in particular frequently describing head and neck injuries. Because of these characteristics, it is important to consider safety measures for students with limited judo experience when learning Ukemi and to take into account differences in neck muscle strength based on gender for the overall safety of judo classes.</p>