A microwave heating device comprising: a heating chamber adapted to house an object to be heated; a microwave supply portion for supplying microwaves to the heating chamber; a waveguide tube for propagating microwaves supplied from the microwave supply portion, to the heating chamber; and a plurality of microwave radiating portions which are formed on the waveguide tube and are for radiating microwaves propagating through the waveguide tube, to inside of the heating chamber; and a heating-chamber input portion which is adapted to direct, to the inside of the heating chamber, microwaves having propagated through the waveguide tube, and having passed through positions where the microwave radiating portions are formed, and which is provided with an opening at a termination end of the waveguide tube in a microwave propagation direction, to realize a state where a progressive wave is dominant, among the microwaves propagating through the waveguide tube; wherein the microwave radiating portions are adapted to radiate, to the inside of the heating chamber, microwaves based on the progressive wave propagating through the waveguide tube, characterized in that the heating-chamber input portion comprises a reflective-surface structural portion formed in a termination end of the waveguide tube in a microwave propagation direction, the reflective-surface structural portion being constituted by a surface inclined with respect to the microwave propagation direction in such a way as to chamfer the termination end; and an inputting opening portion adapted to direct, to the inside of the heating chamber, microwaves having been reflected by the reflective-surface structural portion, and the inputting opening portion is formed in the same plane as that of a microwave-radiating-portion formation surface of the waveguide tube, which is provided with microwave radiating portions. a heating chamber adapted to house an object to be heated; a microwave supply portion for supplying microwaves to the heating chamber; a waveguide tube for propagating microwaves supplied from the microwave supply portion, to the heating chamber; and a plurality of microwave radiating portions which are formed on the waveguide tube and are for radiating microwaves propagating through the waveguide tube, to inside of the heating chamber; and a heating-chamber input portion which is adapted to direct, to the inside of the heating chamber, microwaves having propagated through the waveguide tube, and having passed through positions where the microwave radiating portions are formed, and which is provided with an opening at a termination end of the waveguide tube in a microwave propagation direction, to realize a state where a progressive wave is dominant, among the microwaves propagating through the waveguide tube; wherein the microwave radiating portions are adapted to radiate, to the inside of the heating chamber, microwaves based on the progressive wave propagating through the waveguide tube, characterized in that the heating-chamber input portion comprises a reflective-surface structural portion formed in a termination end of the waveguide tube in a microwave propagation direction, the reflective-surface structural portion being constituted by a surface inclined with respect to the microwave propagation direction in such a way as to chamfer the termination end; and an inputting opening portion adapted to direct, to the inside of the heating chamber, microwaves having been reflected by the reflective-surface structural portion, and the inputting opening portion is formed in the same plane as that of a microwave-radiating-portion formation surface of the waveguide tube, which is provided with microwave radiating portions.