An image forming apparatus comprising: a first image bearing member on which a toner image is to be formed; a second image bearing member (1M, 1C, 1K) on which a toner image is to be formed; a conveying member for carrying and conveying the toner images; a first transferring device for transferring the toner image on said first image bearing member onto said conveying member at a first transfer portion; a second transferring device (TM, TC, TK) for transferring the toner image on said second image bearing member (1M, 1C, 1K) onto said conveying member at a second transfer portion located downstream of the first transfer portion with respect to a movement direction of said conveying member; a conveying member position index formed on a surface of said conveying member along the movement direction of said conveying member by being transferred from said first image bearing member onto said conveying member; image bearing member position indices formed on a surface of said second image bearing member (1M, 1C, 1K) along a rotational direction of said second image bearing member (1M, 1C, 1K); a conveying member position index detecting device (35M, 35C, 35K) for detecting, on the surface of the conveying member, said conveying member position index; an image bearing member position index detecting device (32M, 32C, 32K) for detecting, on the surface of the second image bearing member (1M, 1C, 1K), said image bearing member position indices; an adjusting device (MM, MC, MK, 48a, 48b) for adjusting a rotational speed of said second image bearing member (1M, 1C, 1K) or a position of said second image bearing member (1M, 1C, 1K) with respect to the movement direction of said conveying member; and a controller (110 to 114) for controlling said adjusting device (MM, MC, MK), wherein the controller (110 to 114) is adapted to control so as to adjust a position of an image bearing member position index correspondingly to said conveying member position index which is going to reach the second transfer portion, on the basis of detection results of said conveying member position index detecting device (35M, 35C, 35K) and said image bearing member position index detecting device (32M, 32C, 32K). a first image bearing member on which a toner image is to be formed; a second image bearing member (1M, 1C, 1K) on which a toner image is to be formed; a conveying member for carrying and conveying the toner images; a first transferring device for transferring the toner image on said first image bearing member onto said conveying member at a first transfer portion; a second transferring device (TM, TC, TK) for transferring the toner image on said second image bearing member (1M, 1C, 1K) onto said conveying member at a second transfer portion located downstream of the first transfer portion with respect to a movement direction of said conveying member; a conveying member position index formed on a surface of said conveying member along the movement direction of said conveying member by being transferred from said first image bearing member onto said conveying member; image bearing member position indices formed on a surface of said second image bearing member (1M, 1C, 1K) along a rotational direction of said second image bearing member (1M, 1C, 1K); a conveying member position index detecting device (35M, 35C, 35K) for detecting, on the surface of the conveying member, said conveying member position index; an image bearing member position index detecting device (32M, 32C, 32K) for detecting, on the surface of the second image bearing member (1M, 1C, 1K), said image bearing member position indices; an adjusting device (MM, MC, MK, 48a, 48b) for adjusting a rotational speed of said second image bearing member (1M, 1C, 1K) or a position of said second image bearing member (1M, 1C, 1K) with respect to the movement direction of said conveying member; and a controller (110 to 114) for controlling said adjusting device (MM, MC, MK), wherein the controller (110 to 114) is adapted to control so as to adjust a position of an image bearing member position index correspondingly to said conveying member position index which is going to reach the second transfer portion, on the basis of detection results of said conveying member position index detecting device (35M, 35C, 35K) and said image bearing member position index detecting device (32M, 32C, 32K). wherein the controller (110 to 114) is adapted to control so as to adjust a position of an image bearing member position index correspondingly to said conveying member position index which is going to reach the second transfer portion, on the basis of detection results of said conveying member position index detecting device (35M, 35C, 35K) and said image bearing member position index detecting device (32M, 32C, 32K).