A developer for developing electrostatic latent images is constituted by a toner, and negatively chargeable spherical resin particles having an average particle size of 0.03-1.0 micron and a volume resistivity of 10.sup.6 -10.sup.12 ohm.cm. The toner may comprise toner particles and hydrophobic inorganic fine powder, which is generally used in a larger amount than the negatively chargeable spherical resin particles. The negatively chargeable spherical resin particles function to provide a toner image which is faithful to an electrostatic latent image formed on a photosensitive member while preventing toner-sticking onto the photosensitive member preferably in combination with a contact-charging means for charging the photosensitive member.