To provide a microwave burning furnace that solves a problem that a ceramic fiber board as a thermal insulation member deforms in a burning state, and prevents an accident where the thermal insulation member deforms to sink a burned material in burning.

The microwave burning furnace comprises a furnace body for storing the burned material and a microwave generating means for generating microwave and guiding it to the furnace body. The furnace body has at least a double thermal insulation member, and has porous ceramics having 50-95% of porosity disposed between the lower surface of the bottom of the inside thermal insulation member and the upper surface of the bottom of the outside thermal insulation member. Thus, the microwave burning furnace where the thermal insulation member does not deform in burning and the burned material does not sink is provided.