Each prefecture executes various efforts to achieve an increase in player numbers in competitive swimming and in players' competitive abilities. However, the result is a large difference in each prefecture. This study aimed to examine the change of participation rate in 2010 and 2015 in each prefecture. Participation rate is a result of dividing the number of inter-high school athletic meeting participants by the number of all Japanese high school athletes' federation enrollments for competitive swimming. Progress rate is the difference in participation rate in both years. If a progress rate was positive, it implied that 2015 is superior in terms of participation rate to 2010. Among males, progress rates for Yamagata (+5.0%), Tokushima (+4.3%), Niigata (+4.1%), Okayama (+3.4%), and Fukui (+2.5%) were higher (M+1.0SD); on the other hand, those for Ishikawa (-13.2%), Gunma (-5.3%), Wakayama (-5.3%), Akita (-5.3%), and Mie (-4.8%) were lower. Among females, progress rates for Tokushima (+20.0%), Okayama (+7.8%), Yamagata (+4.9%), Ehime (+4.1%), and Ishikawa (+3.8%) were higher; on the other hand, those for Yamanashi (-9.3%), Okinawa (-9.1%), Kagawa (-7.8%), and Saga (-6.4%) were lower (M-1.0SD).