Due to the recent intensification of work hour regulation by Japanese employers, a large number of engineers in research and development are increasingly unable to put in satisfactory amount of time in work, and the incidences of experiencing non-accomplishment in work are growing. This study investigates whether and how the overtime reduction affects engineers' sense of fulfillment in work and personal life, and examines how they influence engineers' depression and perceived health. Results show that overtime reduction has both positive and negative sides, and while on one hand it enhances the time adequacy for engineers' private life, on the other hand it significantly reduces their sense of fulfillment in work. Furthermore, unbalance such as "non-achievement in work" and "fulfillment in private life" is likely to deteriorate their psychological well-being. Findings suggest that in order to realize engineers' work-life balance it is not sufficient to just enhance the time in private life, but it is also necessary to ensure simultaneously a sufficient time in work.