An optical recording apparatus includes an optical system, a photosensitive drum and a rotational mechanism. Multibeam laser light is focused through the optical system to form an image as a column of image-forming beam spots on the photosensitive drum. The column of image-forming beam spots is arranged obliquely on the photosensitive drum and scanned to perform optical recording. The optical system includes a resolution converting lens system which is detachably attached into the optical system. The rotating mechanism adjusts rotation of the resolution converting lens system around an optical axis thereof. The resolution converting lens system is rotated by the rotating mechanism to change of resolution of the recording image. The resolution converting lens system is attached into and detached from the optical system to change of resolution of the recording image.