an image forming apparatus includes an intermediary transfer member for carrying an image ; a transferring device for transferring the image from the intermediary transfer member onto a sheet ; a device for forming a toner patch for a density adjustment between adjacent sheets , in an area corresponding to between adjacent ones of sheets on the intermediary transfer member ; a detector for detecting density of the patch ; and a sheet interval density adjusting device for adjusting in real time a density / tone - gradation property of the image on the basis of a detection result of the density detector . the patch includes a density detection area , and an outer marginal portion having a density lower than that of the density detection area . the patch forming device changes at least one of a patch image density of the density detection area , a size of the marginal portion and a density of the marginal portion .