A first metal separator of one of adjacent power generation cells and a second metal separator of the other of the adjacent power generation cells are directly stacked together to form a coolant flow field. The first metal separator has a press line protruding toward the coolant flow field, between a fuel gas flow field and an inlet buffer. The second metal separator has a press line protruding toward the coolant flow field, between an oxygen-containing gas flow field and an inlet buffer. The press lines contact each other to limit flow of the coolant into a back surface buffer.