A microwave heating device includes a heating chamber that accommodates an object to be heated, a microwave generator configured to generate microwaves, a wave guide tube configured to guide the microwaves to the heating chamber, and an electromagnetic field distribution adjustment device provided in a predetermined two-dimensional region within the heating chamber. The electromagnetic field distribution adjustment device has a plurality of metal pieces and a plurality of switches. The plurality of metal pieces are arranged to fill the predetermined two-dimensional region. The plurality of switches connect the plurality of metal pieces with one another. A serially connected row of metal pieces is configured by connecting one metal piece among the plurality of metal pieces to at most two metal pieces adjacent to the one metal piece through at least two of the plurality of switches. The present exemplary embodiment can achieve a low-cost electromagnetic field distribution adjustment device that heats an object to be heated more uniformly, while preventing a drop in heating efficiency.