The invention relates to a friction wheel separator for separating bank notes. Said device comprises a separating roller (1) having grooves (2) and retaining wheels (14) which co-operate with said grooves (2). Said retaining wheels (14) are provided with friction regions (14a) and sliding regions (14b), such that both a sliding region (14b) and a friction region (14a) co-operate with each groove (2) of the separating roller (1). One such friction separator is also especially suitable for the longitudinal separation of narrow bank notes and prevents the sheet to be separated from twisting during the separation process.