A microwave oven has an auxiliary cooking device disposed within a cooking chamber for fixing foodstuffs to be cooked. The auxiliary cooking device includes a supporting base placed on the cooking chamber, a coupling member coupled on the supporting base, a main fixing bar on which relatively large foodstuffs are fixed, and a plurality of auxiliary fixing bars on which relatively small foodstuffs are fixed. The main fixing bar is supported on the supporting base or the coupling member. The auxiliary fixing bars are removably mounted on the coupling member.