PURPOSE: To reduce residual warp of recording sheet by inserting a retaining core for spool with effective diameter variable in the central part of a roll shaped recording sheet coiled without use of bobbin, and by increasing the effective dia. of this retaining core when the remaining amount of the sheet becomes small.

CONSTITUTION: When a roll paper 11 wound up without use of bobbin is used in a recording device such as facsimille, spool 12 shall be of such a type having a retaining core 12, whose effective diameter is variable. For ex., the effective dia. can be changed by installing a plurality of springs 13. Thereby, when a paper roll 11 is set, the force required to widen the inner dia. of the paper roll 11 is larger than the force of the springs 13, so that the springs 13 are held in shrunk state. When the remaining amount of paper 11 has become small and the force required to widen the inner dia. of the paper roll 11 has become smaller than the force of the springs 13, the effective outside dia. D2 of the retaining core 121 shall be increased.