A seat fixing device for fixing an air passenger seat to a floor of an aircraft includes at least one fastening rail (10) in the form or a hollow profile, which is provided with a longitudinal channel (14) delimiting the free flanks (16) of the profile on the top part thereof (12) oriented to the seat. The channel includes through openings (18) located in a predetermined modular dimension, which enlarge the free input section and are used for inserting at least one snap-locking part (24) of a locking body (26). The looking body (26) is movable to a clamping position with the profile (16) of the hollow profile (14) by the relative displacement of each snap-locking part (24) in a perpendicular direction with respect to the longitudinal axis (28) of the fastening rail (10). The fixing device provides an eccentric drive (30) of the locking body (26) for carrying out relative displacement, which reduces assembly costs.