An enclosing apparatus for enclosing an enclosure into an envelope at an enclosing position includes a conveyance roller that conveys the envelope to the enclosing position and an envelope conveyance path through which the envelope is conveyed. An enclosing support is disposed in the envelope conveyance path and supports enclosing of the enclosure into the envelope. The enclosing support retracts a flap of the envelope from the envelope conveyance path while the conveyance roller conveys the envelope to the enclosing position.