The aims of this research are to form a research model for negotiations against leisure constraints, serious leisure activity, and the specialization of sports activity, verify the fitness of this model and define the relationship between the variables in the model. This research was taken on a population of 235 people in the commercial sports center in Seoul city in 2010, taking the members by voluntary, and analyzed them with purposive sampling. The research used AMOS 18.0 program to carry out a covariance structure analysis. The conclusions are as follows. First, serious leisure can be experienced when one puts effort in negotiating against the leisure constraints. Second, when one puts effort in negotiating against leisure constraints, progress is made in specialization of sports activity. Lastly, sports activity becomes more professionalized when one experiences serious leisure.