A microwave treatment device includes a plurality of radiation parts, a transmission line, and a plurality of feeding parts. The plurality of radiation parts includes first, second, and third radiation parts, and radiates a microwave. The transmission line has a loop line structure provided with a plurality of branch parts including first, second, and third branch parts, and transmits the microwave to the first, second, and third radiation parts respectively connected to the first, second, and third branch parts. The plurality of feeding parts includes the first feeding part and the second feeding part arranged in the transmission line at an interval of ¼ or less of the wavelength of the microwave, and transmits the microwave to the transmission line. According to this aspect, a radiation part that radiates the microwave can be selectively switched. This enables the intended heating distribution to be achieved.