PURPOSE: To obtain vivid visible images of high quality with less photographic fog by using a mixture of two kinds of magnetic toner which have specific saturation magnetization and average particle sizes.

CONSTITUTION: A one-component insulating magnetic toner consisting essentially of a magnetic powder and an insulating high polymer material is obtained by mixing the first magnetic toner having 30W55emu/g saturation magnetization and 8W15μm average particle size and the second magnetic toner whose saturation magnetization is ≥50emu/g and is larger than that of the first magnetic toner by ≥10emu/g and average particle size is 3W6μm. The first magnetic toner and the second magnetic toner are mixed in (1:3)W(3:1). The first toner which is slightly inferior in resolving power but brings about a high image density and make the occurrence of photographic fog difficult and the second toner which brings about a low image density but is superior in resolving power and makes the occurrence of photographic fog difficult are mixed in said ratio and are used, and respective demerits are compensated to obtain overall well- balanced images. Both toners are consumed equally for development, and uniform images are obtained independently of the number of copies.