The utility model relates to a device for cleaning teeth, particularly a dental floss bar. The utility model is composed of a holding handle and an operation end which has an included angle with the holding handle; the front end of the operation end is a horizontal section; a dental floss is arranged on the most front edge of two convex ribs which are arranged in a bow shape with the operation end; the dental floss and the holding handle are mutually vertically arranged; the dental floss can extend into each tooth gap and close up tooth meat easily; stable vertical push power and pull power can be formed among the tooth surfaces of the tooth gaps by pushing and pulling the holding handle by hands; the dental floss can scrape tooth dirt among the tooth surfaces by the push power and the pull power and by matching with moving the dental floss bar up and down. The utility model especially has an obvious effect on the molar of the inner part of a mouth cavity.