Method for manufacturing bonded body

A method for manufacturing a bonded body, comprising:

• obtaining a first composite that comprises a first outer layer portion located on an outer surface side of the first composite, and containing silicon oxide as a main component of the first composite, and a first inner portion surrounded by the first outer layer portion and containing silicon carbide and silicon;
• obtaining a second composite that comprises a second outer layer portion located on an outer surface side of the second composite, and containing silicon oxide as a main component of the second composite, and a second inner portion surrounded by the second outer layer portion and containing silicon carbide and silicon;
• grinding or polishing a first contact surface at which the first inner portion is in contact with the second inner portion and/or a second contact surface at which the second inner portion is in contact with the first inner portion;
• and
• bringing the first contact surface and the second contact surface into contact with each other and performing thermal treatment in a vacuum atmosphere or an inert gas atmosphere.