PURPOSE: To obtain a one-component type magnetic toner improved in electrostatic chargeability and transfer efficiency and elevated in image density by specifying a range of ratio of toner charge amt. to additive charge amt.

CONSTITUTION: An additive having a function as a triboelectric carrier to a magnetic toner and said magnetic toner chargeable to opposite polarity are used to form a one-component type magnetic toner. A combination of the toner and the additive is selected so as to allow the ratio of the absolute values of A to that of B to satisfy the inequalities as shown on the right, where A, B are each the amt. of charge of the toner and the additive, respectively. As the additive, fine ZnO powder doped with alumina, colloidal silica processed with vinylsilane, etc. are used, average particle diameter in the amt. of 0.1W10wt. based on the magnetic toner, and a desirable average particle diameter os 10W3,000μm.