In this paper, we introduce a further optimization of morphology of compliant joint based on FEM analysis for a compliant-parallel mechanism with a wide working area and a high accuracy. Compliant-parallel mechanism is the mechanism that all joints are composed by compliant joints in a parallel structure. In the integration of compliant and parallel mechanism, the motion of compliant joints can be guided by mechanical constraints from the parallel structure; thus the mechanism can be precisely driven. However, since compliant joints generally have a limited working area due to limitation in their structural deformation, the working area is commonly limited in micrometer-scale. Designing the compliant joints within a wide range of working area presents us a new challenge: the joints should be elastic for the desired direction, but also rigid for non-desired direction to be deformed. From these requirements, the morphology of the compliant joint was optimized by FEM analysis, and newly serially layered-flat spring compliant joint was developed. The developed compliant joint was implemented on a parallel mechanism as a high precision micro-assembly system for optical components. The prototype enabled 50×50×5 mm of working area within 0.71 mm of repeatable accuracy. From these results, the effectiveness of the morphological optimization for compliant joint was shown.