A bonded body 1 includes a piezoelectric layer 11a made of a piezoelectric material, a dielectric layer 12 disposed below the piezoelectric layer 11a, and a support substrate 13 bonded to the piezoelectric layer 11a, with the dielectric layer 12 being sandwiched between the support substrate 13 and the piezoelectric layer 11a. The dielectric layer 12 includes a first silicon oxide layer 12a in contact with the piezoelectric layer 11a, and a second silicon oxide layer 12b that is positioned closer to the support substrate 13 than the first silicon oxide layer 12a is. The content of argon contained in the first silicon oxide layer 12a is larger than the content of argon contained in the second silicon oxide layer 12b. Consequently, a bonded body in which peeling of the piezoelectric substrate is unlikely to occur and a method for producing a bonded body are provided.