developing roller 35 when a positively charged developer is used the roller 35a and the sleeves 36c are connected to a negative side of an applying unit 37a through slidable electrodes 40a respectively on the other hand the sleeves 35c and the roller 36a are respectively connected to a positive side of the applying unit 37a through slidable electrodes 40b in fig5 reference numeral 45 denotes a gap regulating roller for regulating a gap l between the developing roller 35 and the regulating roller 36 the gap regulating roller 45 is coaxially and rotatably provided with the regulating roller 36 a circumferential surface of the gap regulating roller 45 abuts against the surface of the developing roller 35 thereby maintaining a distance between centers of the rollers 35 and 36 at a predetermined value however if the developing roller 35 and the regulating roller 36 are satisfactorily supported between the side frames 32 and 33 the gap regulating roller 45 is not necessary the operation and effect of the developing apparatus of this embodiment will now be described when the applying mechanism 37 is operated a negative polarity is provided to the roller 35a of the developing roller 35 and the sleeves 36c of the regulating roller 36 and a positive polarity is provided to the sleeves 35c and the roller 36a for this reason when for example a positively charged developer t is rushed between the developing roller 35 and the regulating roller 36 the developer t is electrostatically attracted onto the development region a of the developing roller 35 as shown in fig6 on.