An image forming apparatus using the laser scan method or the LED method, which is capable of reducing a variation of spot diameter with a simple mechanism, and of forming a high-quality image by adjusting the density depending on the image resolution with a low cost. The image forming apparatus forms an image by developing an electrostatic latent image formed by irradiating a charged photoconductor with light emitted from a light source with developer. A detecting unit detects a distance between an attention pixel and an adjacent image that is adjacent to an image including the attention pixel across a white background. An adjustment unit adjusts a density of the attention pixel based on the distance measured with the detecting unit and a spot diameter of the light on a surface of the photoconductor.