A method and an apparatus of inserting insert or enclosure material into successive envelopes are disclosed. According to the envelope inserting method, the insert material is conveyed along a straight path successively to an envelope inserting position where the insert material is inserted into the envelope and the stuffed envelope is then conveyed out of the inserting position in the same direction as the above straight path. The method includes providing immediately above the envelope inserting position an envelope storage station where a plurality of envelopes are stored in a stack one above another with the front panel of each of the envelopes facing upward so that the envelopes in the storage station are fed successively to the envelope inserting position for insertion thereinto of insert material. Feeding of the envelopes is performed by means of a vertically disposed rotatable screw-like spiral member located at the downstream side of the envelope storage station as seen in the direction in which the insert material is conveyed. The spiral member has formed in the periphery thereof a spiral groove for receiving therein the bottom edges of the respective envelopes, thereby holding such envelops at the bottom edges thereof such that the bottom edges are separated one from another. The spiral member is rotatable in such a direction that causes the bottom edges of the envelopes to move downwards with the rotation of the spiral member and then to be released successively from the holding by the spiral member.