An oven having a partition unit to partition a cooking space into a plurality of independent cooking chambers wherein the partition unit has a heat-insulating structure to prevent heat transfer between the respective cooking chambers. The oven comprises a cabinet, a door to open and close an opened front surface of the cabinet, a partition unit to partition the interior of the cabinet into a plurality of independent cooking chambers, and electric heaters mounted in the cooking chambers. The partition unit includes first and second heat-insulating layers opposite to each other and an air layer disposed between the first and second heat-insulating layers. An inlet and an outlet are formed at the air layer, and a blowing fan is mounted at the inlet. Bent guide members are disposed in the air layer to guide air such that the air uniformly flows throughout the air layer.