The invention is related to improvements in a cooking appliance equipped with both a microwave heating means and a hot air circulation heating means. By controlling the rotational speed of an air circulating fan or the power of heater means according to the kind of food to be cooked, the cooking time is shortened and the quality of cooked food is improved. The hot air discharging section of such an oven includes a perforated plate so as to prevent leakage of microwaves from the heating chamber, and an air baffle means is provided strategically in the hot air discharging section to ensure a uniform distribution of temperature within the heating chamber. The invention also includes an improved relative position of the air inlets, a double-deck tray and the air baffle means which functions to prevent a substantive dehydration of food which is a drawback of a conventional hot air circulation heating system.