Disclosed herein is a fuel cell stack with improved manufacturing performance. The fuel cell stack includes: a separator that comprises a diffusion part, as being provided with a diffusion channel, configured to distribute reaction gas and cooling water and a reaction part, as being continuously formed from the diffusion part and provided with a reaction channel that has a height greater than that of the diffusion channel, configured to move reaction gas distributed from the diffusion part and generate electrons by a chemical reaction; and a gas diffusion layer configured to contact the separator at the diffusion part and the reaction part.