Research on school bullying has tended to focus on its prevalence or frequency while ignoring its perceived severity. This study attempted to construct a perceived School Bullying Severity Scale (SBSS). The original 24-item instrument, revised from the Victim Scale of the School Bullying Scales, covered the four categories of physical, verbal, relational and cyber bullying. The partial credit model was used to conduct Rasch analysis with ConQuest software on data derived from two samples of Taiwanese secondary school students. Sample 1 and sample 2 consisted of 605 and 869 students, respectively. Three items were deleted after examining the quality of the data from sample 1. The reliability and validity of the 21 items on the final scale were verified using data from sample 2. Results demonstrated the reliability and validity of information collected by the SBSS. This study also found that secondary school students rated relational and cyber bullying as more severe than physical and verbal bullying. Differences between teachers' and students' perspectives on the perceived severity of various bullying behaviours as well as implications for preventing and intervening in bullying are discussed. (Contains 1 table and 2 figures.)