To provide a collate envelope preparing device enabling easy production of envelopes.

A lengthwise direction carrying part 30 includes: a lower front cover-enclosed material adhesive application part 34 applying an adhesive 3a to a left side edge 3L of a lower front cover 3 along the lengthwise direction Y; a lower front cover-enclosed material laminating part 35 making the lower front cover 3 and an enclosed material 4 adhere to each other by the adhesive 3a to prepare a laminated body 5; a first lower front cover-upper front cover adhesive application part 37 applying an adhesive 3b to a right side edge 3R of the lower front cover 3 of the laminated body 5 along the lengthwise direction Y; and an enclosed material-upper front cover adhesive application part 38 applying an adhesive 4b to a left side edge 4L of the enclosed material 4 of the laminated body 5 along the lengthwise direction Y. A horizontal direction carrying part 40 includes: a second lower front cover-upper front cover adhesive application part 43 applying an adhesive 3c to upper and lower edges 3D, 3U in the lengthwise direction Y of the lower front cover 3 of the laminated body 5 along the horizontal direction X; and a laminated body-upper front cover laminating part 44 making an upper front cover 2 and the laminated body 5 adhere to each other by the adhesives 3a, 4b, 3c, 3d to prepare the envelope 1.