The present invention provides a fuel cell, including a composite bipolar plate and gasket connecting bipolar plate. A sub-channel is assembled at a concave side of the gasket corresponding with bipolar plate. Main channels of gas running through both sides of the bipolar plate are arranged at separation positions between the bipolar plate and gas sub-channel. The main channels of gas and the gas sub-channel are connected through the channel. The airtight layer is assembled between the bipolar plate and gasket. With the airtight layer, the bipolar plate and gasket can be locked and fixed together steadily and tightly, so that the spaces of flow channels for different fuels can be definitely separated, without any leakage and mistaken mixture.