This study aims to examine the role of job demands on employees’ job performance. Using a sample of 183 employees, the study investigated the impact of four variables of job demands including quantitative, problem solving, attention and responsibility demands on two variables of employees’ job performances such as task and contextual performances. Structural equation modeling analyses showed that the variables of job demands have negative and significant impact on employees’ job performances. The construct of job demands was designed as designed as second-order construct. The analysis from the second order model is utilized to examine the relationship between the independents variables of job demands and job performance. To validate the second-order formative construct model of job demands, alternative models were established for comparison with relative fit.