An image is formed by dividing rasterized original image data into regions in accordance with N recording heads, and scanning a recording body by simultaneously irradiating recording beams from the N recording heads. Corrected image data divided into regions in accordance with the recording heads are generated by changing the rasterized original image data based on information including positional displacements of the recording beams, so that the positional displacements are corrected. Scanning information is generated based on the positional displacement information. The scanning information includes positions and orders for the recording beams to scan the recording body to record the corrected image data.