1. An image forming apparatus, comprising: a light source comprising a plurality of light emitting points; a photosensitive member configured to rotate in a first direction so that a latent image is formed on the photosensitive member by light beams emitted from the light source; a deflection unit configured to deflect the light beams emitted from the light source with a mirror face and cause light spots of the light beams radiated on the photosensitive member to be moved in a second direction orthogonal to the first direction to form scanning lines; a storage unit configured to store information on positional deviation of the plurality of light emitting points in the first direction and information on an optical face tangle error of the mirror face of the deflection unit in accordance with the second direction; a correction unit configured to correct the information on the optical face tangle error stored in the storage unit, based on a deviation amount from a predetermined distance between the deflection unit and the photosensitive member; a calculation unit configured to calculate a positional deviation amount based on the information on the positional deviation stored in the storage unit and the information on the optical face tangle error corrected by the correction unit; a transformation unit configured to transform a position of a pixel of an input image by performing coordinate transformation based on the positional deviation amount calculated by the calculation unit so that an interval between the scanning lines on the photosensitive member becomes a predetermined interval; and a filtering unit configured to obtain a pixel value of a pixel of an output image by subjecting a pixel value of the pixel of the input image to a convolution operation based on the position of the pixel of the input image after the coordinate transformation.