Disclosed herein is a separator for a molten carbonate fuel cell, the separator including four steel sheets in which edges of the four steel sheets are joined to each other thereby providing three spaces therebetween, comprising a cathode channel, serving as a flow path of oxidant gas, formed in the first space; an anode channel, serving as a flow path of fuel gas, formed in the second space such that the anode channel is separated from the cathode channel; and a fuel gas reforming channel formed in the third space, which is located between the first space and the second space. The separator for a molten carbonate fuel cell is advantageous in that the volume of the fuel cell is decreased, and the structure thereof is simple, thus reducing the production cost thereof.