The present invention performs density adjustment (ATR process) and transfer voltage control (ATVC) in parallel; the ATR process transfers and forms a patch image on an intermediate transfer member and detects and adjusts the density of the patch image, and the ATVC gradually raises a transfer voltage to measure a transfer current and generates a transfer voltage corresponding to a target transfer current to control a transfer of an image from an image carrier to the intermediate transfer member. The present invention determines the timing at which the patch image is formed in the density adjustment, in association with the transfer voltage in the transfer voltage control step, to allow a density adjustment process based on density adjustment and transfer voltage control to be executed in parallel.