PURPOSE: To make it possible to automatically correct skews of sheets accumulated in an impeller, by controlling the motion of a skew correcting lever for feeding sheets into the impeller in accordance with the widths and skew angles of the sheets, which are computed.

CONSTITUTION: When sheets 12 such as bank notes or the like are conveyed into a conveying passage 24 in a skew condition, a time difference occurs between the times of passing the light emitting and receiving sections 8, 10, 9, 11 of a sensor section, and therefore, a computing and control circuit 16 calculates the skew angles, lengths and intervals of the sheets 12 in accordance with the above-mentioned time difference, the distance between the sensors and the conveying speed of the sheets 12. Further, if the correction of a skew is required in view of judgment by a skew data memory device 18, the times of arrival of the sheets at impellers 13, 14, the time of passing of the leading end of the sheet 12 to be pushed in by skew correcting lever 3, 4 are calculated so as to rotate the latter, and the times of arrival of the sheets 12 at the impellers 13, 14 are transmitted to an impeller control circuit 19. Thus, it is possible to automatically correct the skews of sheets accumulated in the impellers.