This study is aimed at describing the library service quality of State Institute for Islamic Studies (IAIN) Sunan Kalijaga Yogyakarta from the point of view of users, and at finding out factors influencing it. This description is really important in order to be able to develop it, as the supporter of realizing the three responsibilities of university or institute, namely education, research, and social service. This study uses a descriptive qualitative approach of survey method. Sampling is taken from the group of library users numbering 338 people, and 50 of library staffs. Whereas data collecting is conducted through library research, field research consisting ofdocumentation, questionnaire, and interview The data is organized in tables offrequency and percentage distribution, and it is then described. Based on the service quality concept quoted from the decision of minister of state apparatus empowerment no. 8l of L993, there are ten indicators of service quality namely simplicity, clarity and certainfy,o pennesse, fficiency, economy,f air distribution, punctuality, physical facility, capacity and staff attitude. The result of study indicates that the library service quality of IAIN Sunan Kalijaga yogyakarta based on of users opinion is generally good. This conclusion is based on the mean result7O.247o of the users have good opinion about the indicators of the library service quality. Factors influencing the library service quality are organization climate (87.007o),s upervisions ystem( 68.67Vo)a, nd bureaucracys tructure( 85.337o)A. lthough the serviceq uality at the IAIN Sunan Kalijagas Library is in general good, there are things to consider. The first is about library location which is, accarding to the majority of users, not strategic. The second, is the necessity of developing service security and comfortable service The third is the necessity ofdeveloping reliable physical facilities. Lastly, it is necessary to develop library collection both in quantity and in quality taking the needs of new departments and study programs into consideration.