The present invention provides a fuel cell stack which can reduce variation in temperature distribution of whole cells by a simple change in the structure of a coolant inlet manifold and a coolant outlet manifold in the fuel cell stack without the use of a conventional insulator, which increases the thickness of the fuel cell stack, a heater, which requires a power supply and its control logic, or a cover for forming an air layer for thermal insulation, which disadvantageously prevents the heat generated in the electrode from being transferred to the end plate. The invention provides a fuel cell stack with improved temperature uniformity, comprising one or more coolant flow guide members positioned within a coolant outlet manifold and/or a coolant inlet manifold, which causes coolant present in the coolant outlet manifold to be recirculated to the coolant inlet manifold and then back through one or more predetermined cells adjacent to the end plate to the coolant outlet manifold, thereby providing uniformity in the heat of the fuel cell stack.