PURPOSE: To detect the remaining quantity of roll paper, which is various in size, by means of the same remaining quantity detecting device by varying the position of a shaft core within a bearing in correspondence to the diameter of the shaft core in such a manner that the position of the periphery of the roll paper, the remaining quantity of which varies in correspondence to the diameter of the shaft core, becomes constant with respect to the position of the detecting sensor.

CONSTITUTION: Flange parts 23, 24 of roll shaft cores 23a, 24a for winding the recording paper, which is different in size, are supported in a freely rotatable manner on a recessed, engaging part 7d of a shaft member 7 and another recessed, engaging part of the shaft member, respectively. The diagram on the shows the winding roll peripheral positions 23b, 24b indicating the remaining quantity, for example 50m, of the winding rolls, whose shaft cores are 23a, 24a, ion addition to the positions 22b, 24b of detection rollers corresponding to winding roll remaining quantity 50m and 0(zero)m detected by a detecting lever. The peripheral positions 23b, 24b corresponding to the time of the remaining quantity of the two winding rolls being 50m and the peripheral positions 23a, 24a corresponding to the time of the remaining quantity being 0m are obtained by calculation. Then, the positions of the centers 01, 02 of two shaft cores 23a, 24a are determined so that the peripheral positions 23b and 24b and 23a and 24a take the same position as the detecting positions 22a and 22b.