To produce a letter so as to prevent contents from being moved in an envelope.

The letter producing apparatus comprises: an enclosing part configured to fold envelope paper 100 provided with an adhesive part 110 (re-wet glue 110b) to be formed into an envelope 150, or content paper 30 to serve as contents 50, to convey the envelope paper 100 and content paper 30 to a prescribed enclosing position, and to enclose the content paper 30 into the envelope paper 100; and a sealing part configured to stick the re-wet glue 110b on the envelope paper 100 with the content paper 30 enclosed therein. The prescribed enclosing position is the position in which the re-wet glue 110b on the envelope paper 100 and the content paper 30 come into contact with each other. The apparatus is provided with control means which controls the enclosing part to adjust the amount of the envelope paper 100 and the contact paper 30 so as to be conveyed to the prescribed enclosing position.