Degradation of solid oxide fuel cells caused by non-uniformity of physical properties such as temperature, pressure and species concentrations, attributed to thermo-electrochemical reaction, is a critical problem for both stack performance and durability. To improve the internal uniformity, a new manifold and flow channel design is devised and introduced in this study. The main goal of this study is to observe improvements of mass flow distribution and analyze thermal effects of the new design compared to a conventional design with parallel channels and cross-flow pattern. To conduct numerical simulation, a physical model that resolves the three-dimensional structure of a planar, solid oxide fuel cell and describes internal heat generation through heat box assumption is used. It is confirmed that difference between the maximum temperature and the minimum temperature of a unit-cell decreases from 94.4℃ to 56.0℃, and mass flow distribution is also formed as intended.