In analyzing job search behavior, most literature usually consid-ers either employment search or unemployment search, and com-pares the difference of search efficiency separately. However, whena young man first goes into the job market, he might quickly finda low-salary job, and then applies on-the-job search to switch toa better job. The young man may also insists on finding a decentjob before he starts his job at all, otherwise he prefers to be unem-ployed for a while. Therefore, on-the-job search and unemploymentsearch may be substitutible. If we estimate one search behavior and neglect the other; we may get a biased estimation owing to misspacification. Applying the nested logit model. This study estimatesthe two search, behaviors simulataneonsly. and computes the degreeof subsitution between them. Using a data set of college graduatesin Taiwan, we find that there is a significant substitution betweenthe two types of search.