The present invention provides a startup control device and method for a fuel cell system. The startup control device includes a concentration meter, a hydrogen feed rate controller, and a controller. The concentration meter measures the concentration of oxygen located in the anode of a fuel cell stack. The hydrogen feed rate controller is disposed at an inlet of the anode. The controller receives an oxygen concentration signal value from the concentration meter while controlling the hydrogen feed rate controller to adjust a hydrogen feed rate to the anode.