To reduce a cost through reduction of the number of parts by a method wherein a cooking chamber is partitioned and comprises a partition wall member to form an electrical equipment mounting part and a bottom plate covering a bottom fase side of the cooking chamber and disposed on one side of the partition wall member.

Cooking chamber 110 is partitioned and a bottom plate 200 is arranged at the inside of a partition wall member 100, by which an electrical equipment mounting part 120 is bent to complete the cooking chamber 110. Thereafter, a high frequency generating means 17 is mounted on an electrical equipment mounting part 120, a magnetron 19 and a wave guide 21 are disposed on the upper side of the partition wall member 100, and a rear plate 7 is disposed on the rear side of the partition wall member 100, and thereafter, a front plate 9 is disposed on the front side of the partition wall member 100. In a so assembled microwave oven, by integrally forming the electrical equipment mounting part 120 wherein electrical equipment is mounted by the partition wall member 100, assembly ability is improved, a material cost is reduced, and thus a cost is reduced through reduction of the number of parts.