An image forming apparatus includes: a latent image forming unit forming a latent image; a transfer body on which a reference index for setting an output start time point of image data is formed; a detecting unit outputting a detection signal changing according to passing of an adhesion material on the transfer body; a controller that starts a first period during which change of the detection signal is ignored, according to first change of the detection signal, starts a second period after the first period, regards second change of the detection signal occurring first in the second period as a reference of the output start time point, and ignores change of the detection signal after the second change, to control outputting the image data; and a cleaning information outputting unit outputting information on cleaning the transfer body according to the number of changes of the detection signal in these periods.