Although it has been suggested that social network site (SNS) use motives are one of important determinants of SNS addiction, there has not been yet a scale to assess them. The aim of this study was to examine psychological properties of a newly developed Social Network Site Use Motives Scale (SUMS) in a college student sample. The SUMS was administered to 481 nonclinical participants. Exploratory factor analysis, internal consistency analysis, and correlation analysis were undertaken to examine its validity and reliability. Results of factor analysis indicated that the SUMS consisted of four factors. Indices of internal consistency reliability, test-retest reliability, and criterion validity of SUMS were acceptable. Our study suggested that SUMS could be used as an effective tool to assess SNS use motives. The usage of SUMS should be encouraged in future studies of SNS use motives. Future research using this measure could provide a more comprehensive model of the relationship between SNS use motives and SNS addiction.