A document handler is provided that comprises a validator 2 having a main conveyor 4, a stacker 3 having a storage 50 detachably attached to validator 2, a storage conveyor 5 in storage 50 for stowing a document fed from validator 2 into storage 50 and picking out the document stored in storage 50 to validator 2 through main conveyor 4 to issue picked document from validator 2, a reversible motor 70 in main conveyor 4 drivingly and detachably connected to storage conveyor 5 of storage 50.