An image forming apparatus, comprising: at least one photoconductor wherein an image is formed on the at least one photoconductor; an intermediate transfer member including an image formation area, and a scale which includes a plurality of concave and convex portions is located at a position outside of the image formation area and on an inner circumference of the intermediate transfer member; a drive device configured to drive the intermediate transfer member; a developing device configured to form an image on the at least one photoconductor; a first transfer device configured to transfer the image from the at least one photoconductor on the image formation area of the intermediate transfer member, a second transfer device configured to transfer the image on the image formation area to a recording sheet; and a sensor disposed on the internal circumference of the intermediate transfer member and configured to detect the scale on the intermediate transfer member and to output a signal corresponding to the detection of the scale, characterized in that the sensor and the scale are arranged at a predetermined non-zero distance from one edge of the intermediate transfer member being nearest to the location of the scale, wherein the scale is located at a first distant (b) from one edge of the image formation area being nearest to the location of the scale and located at a second distant (a) from the one edge of the intermediate transfer member being nearest to the location of the scale and wherein a reading gap exists between the sensor and the scale. at least one photoconductor wherein an image is formed on the at least one photoconductor; an intermediate transfer member including an image formation area, and a scale which includes a plurality of concave and convex portions is located at a position outside of the image formation area and on an inner circumference of the intermediate transfer member; a scale which includes a plurality of concave and convex portions is located at a position outside of the image formation area and on an inner circumference of the intermediate transfer member; a drive device configured to drive the intermediate transfer member; a developing device configured to form an image on the at least one photoconductor; a first transfer device configured to transfer the image from the at least one photoconductor on the image formation area of the intermediate transfer member, a second transfer device configured to transfer the image on the image formation area to a recording sheet; and a sensor disposed on the internal circumference of the intermediate transfer member and configured to detect the scale on the intermediate transfer member and to output a signal corresponding to the detection of the scale, characterized in that the sensor and the scale are arranged at a predetermined non-zero distance from one edge of the intermediate transfer member being nearest to the location of the scale, wherein the scale is located at a first distant (b) from one edge of the image formation area being nearest to the location of the scale and located at a second distant (a) from the one edge of the intermediate transfer member being nearest to the location of the scale and wherein a reading gap exists between the sensor and the scale.