A timing detection device for detecting timing of movement of a photoreceptor drum or an intermediate transfer belt of an image forming apparatus, the timing detection device comprising: a moving object which is a disk member including a first face and a second face placed opposite to the first face, has a predetermined thickness between the first face and the second face, and in which the first face and the second face are movable in a moving direction that is parallel to the first face and the second face, the moving object being rotatable in a rotating direction, as the moving diretion, around a predetermined rotating axis; a plurality of openings which are formed by penetrating the moving object from the first face to the second face, and disposed with a spacing along the moving direction, the openings being a plurality of slits that are opened with a spacing in a circumferential direction and opened along an axial direction of the rotation in the disk member; a sensor unit configured to emit detection light from the first face side toward the moving object, and to receive the detection light that passes through the openings on the second face side; and a timing detection unit configured to detect timing of movement of the moving object based on a pulse signal of the received detection light; wherein in a cross sectional view including the moving direction of the moving object and a thickness direction of the moving object from the first face toward the second face, the moving object includes: an inner wall part which demarcates a lateral edge of the openings on an upstream side or a downstream side in the moving direction, the inner wall part blocking the detection light emitted from the sensor unit; and an edge part which protrudes toward the downstream side or the upstream side in the moving direction at an end fringe part on the first face side or the second face side of the inner wall part, characterized in that the inner wall part demarcates a lateral edge of the openings on the downstream side in the moving direction and, in the cross sectional view, the inner wall part inclines so that the second face side is disposed further toward the upstream side in the moving direction than the first face side, the edge part is formed at an end fringe part on the second face side due to the inclination of the inner wall part, and the timing detection unit is configured to detect the timing of movement based on a change from a state of the detection light being blocked by the edge part to a state of the detection light passing through the openings as a result of the movement of the moving object. a moving object which is a disk member including a first face and a second face placed opposite to the first face, has a predetermined thickness between the first face and the second face, and in which the first face and the second face are movable in a moving direction that is parallel to the first face and the second face, the moving object being rotatable in a rotating direction, as the moving diretion, around a predetermined rotating axis; a plurality of openings which are formed by penetrating the moving object from the first face to the second face, and disposed with a spacing along the moving direction, the openings being a plurality of slits that are opened with a spacing in a circumferential direction and opened along an axial direction of the rotation in the disk member; a sensor unit configured to emit detection light from the first face side toward the moving object, and to receive the detection light that passes through the openings on the second face side; and a timing detection unit configured to detect timing of movement of the moving object based on a pulse signal of the received detection light; wherein in a cross sectional view including the moving direction of the moving object and a thickness direction of the moving object from the first face toward the second face, the moving object includes: an inner wall part which demarcates a lateral edge of the openings on an upstream side or a downstream side in the moving direction, the inner wall part blocking the detection light emitted from the sensor unit; and an edge part which protrudes toward the downstream side or the upstream side in the moving direction at an end fringe part on the first face side or the second face side of the inner wall part, an inner wall part which demarcates a lateral edge of the openings on an upstream side or a downstream side in the moving direction, the inner wall part blocking the detection light emitted from the sensor unit; and an edge part which protrudes toward the downstream side or the upstream side in the moving direction at an end fringe part on the first face side or the second face side of the inner wall part, characterized in that the inner wall part demarcates a lateral edge of the openings on the downstream side in the moving direction and, in the cross sectional view, the inner wall part inclines so that the second face side is disposed further toward the upstream side in the moving direction than the first face side, the edge part is formed at an end fringe part on the second face side due to the inclination of the inner wall part, and the timing detection unit is configured to detect the timing of movement based on a change from a state of the detection light being blocked by the edge part to a state of the detection light passing through the openings as a result of the movement of the moving object.