Objective: Smartphone use is pervasive among youth in Japan, as with many other countries, and is associated with spending time online and on social media anywhere at any time. This study aimed to test a Japanese version of the Smartphone Addiction Scale-Short Version (SAS-SV) among Japanese college students. Methods: The subjects of this study were 602 college students in Japan. The study questionnaire consisted of questions about demographics (age, gender etc.), possession of a smartphone, internet use [length of internet use on weekdays and weekend, favorite social networking service (SNS) etc.], Young’s Internet Addiction Test (IAT), and the Smartphone Addiction Scale-Short Version (SAS-SV) translated into Japanese. Results: There was a total of 573 respondents (180 male, 393 female) who completed the questionnaire (mean 19.3±1.3 years). LINE was the most popular social media platform (52.0%) followed by Twitter (36.3%). The overall Internet Addiction Test (IAT) score was 45.3±13.2, with 4.5% classified as having severe addiction (IAT ≥70). The mean SAS-SV scores were 24.4±10.0 for males and 26.8±9.9 for females. Based on proposed cutoff scores, 22.8% of males and 28.0% of females screened positive for smartphone addiction. The total scores of the SAS-SV and the IAT was correlated significantly. Conclusion: As the number of smartphone users becomes higher, problems related to smartphone use also become more serious. Our results suggest that the Japanese version of SAS-SV may assist in early detection of problematic use of smartphones.