Excessive workplace stress affects the individual's health as well as social collaborations, so the management of stressors is essential. However, an individual worker who only subjectively reflects on his or her individual and social stressors may misinterpret them, and thus not be able to manage them. This paper aims at engaging workplace stress reflection on objective stress-related physiological data using a shared display, which provides an anonymous view of the individual stress-related physiological signals (i.e., heart-rate variability) through a collective visualization. A minimalist proof-of-concept system is implemented for investigating the design space and deployed during group collaboration. The user study results show that the visualization successfully drew the participants' awareness and increased their understanding of self and organizational stress. This work highlights the importance of objective physiological data in the reflection process of organizational stress management.