A fixing device includes a cylindrical film a pressing member, and a preventing member including a preventing surface configured to prevent movement of the film in a longitudinal direction, and a film rotation guiding surface. As viewed in the longitudinal direction of the film, the preventing surface includes first and second regions positioned downstream and upstream, respectively, of a nip center line with respect to a recording material feeding direction. The first region retracts from a longitudinal film end surface relative to the second region. The second region continuously extends in the recording material feeding direction from a portion upstream of the nip center line to a portion downstream of the nip center line, and has a length, with respect to a rotational direction of the film, that is greater at the portion upstream of the nip center line than at the portion downstream of the nip center line.