To supply a wrapping material properly by preliminarily delivering the wrapping material continuously, and to improve working environment and economy by eliminating the braking mechanism of a supply reel.

The amount of a wrapping material F stored in a suction chamber 3 (storing means) is detected step by step by each of a lower-stage sensor 11, a middle-stage sensor 12, and an upper-stage sensor 13. It is thus possible to recognize whether or not there is too much or too little storage amount of the proper wrapping material F step by step. A central control part 15 variably-control the speed of preliminary delivery by a preliminary delivery motor 4 according to the storage amount.