Reversal development method of electrostatic latent image by the use of high-resistivity magnetic toner

A reversal development method of visualizing an electrostatic latent image through development, comprising the steps of:

• forming a magnetic brush around an outer circumferential surface of a developing sleeve accommodating a magnet therein, by the use of a developer composed of high-resistivity magnetic toner having a resistance value of 10.sup.13 .OMEGA.cm or more under an electric field of 10.sup.4 V/cm and a charge amount of 5 to 15 .mu.Q/g per unit mass generated by gaseous discharge;
• rubbing a surface of an electrostatic latent image carrier bearing said electrostatic latent image with said magnetic brush;
• and
• applying simultaneously to said magnetic brush during said rubbing, an a.c. bias, and a d.c. bias approximately equal to a sum of a potential of an image portion of said electrostatic latent image and a potential of a non-image portion thereof.