An image forming apparatus has an electrostatic latent image bearing member capable of bearing an electrostatic latent image thereon, and a developer apparatus having a developer material for visualizing the electrostatic latent image into a visualized image. The developer apparatus includes a developer material bearing member, a housing adapted to accommodate a developer material, and a supply roller adapted to supply the developer material within the housing for the developer material bearing member. The supply roller has an outer circumferential foam layer. The foam layer is made of resin foam or rubber foam and has an air permeability of 5 ml/cm.sup.2/s or less, a density of 50-200 kg/m.sup.3, and a hysteresis loss ratio of 35-45%.