To facilitate insertion of sealing contents into an envelope.

This insertion assistance for sealing contents is composed of an inserting base which has a tongue part formed at the tip, raised a little from a basal plane and capable of being inserted into the envelope coming near on the basal plane and is capable of bearing the contents to be inserted into the envelope, and of a plate-shaped insertion guide which is provided rotatably on the insertion base, with the tip set at that of the tongue part or a little behind it of which the inserting portion at the tip is inserted when the tongue part is inserted into the envelope and of which the top side is formed to be higher gradually backward.