PURPOSE: To prevent printing inferiority or the erroneous reading of magnetic data by returning a passbook to a passbook taking-in port when skew of a prescribed value or more is detected by a skew detection means.

CONSTITUTION: A skew detection means 11 has a lateral shift mechanism 41 laterally shifting a passbook A toward the reference guide 40 provided along one side of a feed path 9a and a skew sensor 42 consisting of a light emitting element 42a and a photodetector 42b. The laterally shifted passbook A' is fed to the deep part of the apparatus and a magnetic strip S is scanned by a magnetic head 10 and data is read. At this time, the number of the driving steps of a stepping motor 8 is counted in the quantity corresponding to predetermined feed quantity l4. The skew sensor 42 arranged at a fixed distance l3 in the guide 40 executes detection operation and judges 'feed skew is within a prescribed value if dark' and 'feed skew of the prescribed value or more is generated if bright' and returns the passbook to an access port 3 with the reverse rotary operation of roller pairs 7....