工作者的不安全行為，常是造成職業災害或工作意外的主因，而個人特徵與作業情境則是其重要的影響要素。因此，本研究以個人與情境互動的角度，針對國內高工作風險的營造業，探討工作者內外控信念與主管支持對其不安全行為的影響效果。本研究以1208位本地全職營造業勞工為受試者，研究結果發現：(l)內外控信念對不安全行為具有顯著的預測效果，內控信念越高或外控信念越低的勞工，其不安全行為的展現程度越低。(2)主管支持能有效預測勞工的不安全行為，當勞工知覺的主管支持越高時，其不安全行為的展現程度就越低。(3)主管支持除了具主要預測效果外，並可調節外控信念與不安全行為間的關係，但對內控信念則不具有之。最後，本文依據研究結果，針對工作安全理論與實務管理意涵，作進一步之探討。 There is a popular notion that workers' unsafe behaviors are the primary causes of workplace accidents, and a number of researchers suggest a perspective that highlights the influences from individual characteristics and situation factors. Thus, the aim of this study was to examine the effects of locus of control and supervisory support on unsafe behavior in the workplace. Particularly, we were interesting in individual differences in the impact of perceived supervisory support on unsafe behavior between workers with an internal versus an external locus of control. Data were collected from 1208 workers in construction industry in Taiwan. The results indicated that locus of control were significantly associated with unsafe behaviors. Workers with higher external locus of control appeared higher levels of unsafe behaviors; those with higher internal locus of control appeared lower level of unsafe behavior. In addition, supervisory support was negatively related to unsafe behavior. It seems that when workers perceived their supervisor's support, an implied obligation for job safety develops. Thus, supervisory support had the function to reduce workers' unsafe behavior. Furthermore, supervisory support was found to moderate the relationship between external locus of control and unsafe behavior. For internal locus of control, no moderating effect of supervisory support was found. Finally, theoretical and practical implication of job safety and the possible direction of future research were also discussed.