The researcher used descriptive qualitative research method in order to achieve the research aim. In this research was conducted by using Quantitative-Qualitative data which it was the use of descriptive qualitative method. The main purpose on this study is about to find out what is students’ perceptions towards plagiarism in writing assignment. It was aimed to know about students’ perception towards plagiarism in writing ability and also the reasons
why did the students’ do plagiarism. This research conducted not to all English students’ of IAIN SAS Bangka Belitung as a respondents.The research respondents were the students’ of the third semester class B, fifth semester class A, seventh semester class B, ninth semester class A and class B from English Education with total 92 numbers of the students’. In collecting the data of the research was using questionnaires and interviews. In the questionnaire it showed the data for students’ perceptions towards plagiarism on their writing ability on perception’s effect was 50%, for the reasons’ effect was 64%, and 71% for the
students’ knowledge effect. From the result revealed that most of the students’ are already know and understand about what plagiarism is. Most of the students think that plagiarism has a bad impact for their writing ability because once they did it they addicted for do it repetitively. In another hand for the reasons why did the students’ do plagiarism is because of a lack of time, they are too lazy, they don’t have any idea about the assignment, and their environment.