The rotation speed of an intermediary transfer belt 41 when it is brand-new is stored as a reference rotation speed. Registration patches Rk to Ry are formed to calculate displacement amounts, and based on the rotation speed difference between the rotation speed of the intermediary transfer belt 41 and the reference rotation speed, the calculated displacement amounts are corrected into displacement amounts expected when the secondary transfer roller 42 is contacted with the intermediary transfer belt 41. Next, based on the corrected displacement amounts, the positions at which exposing devices 60K to 60Y form electrostatic latent images are corrected. Thus, registration correction can be performed accurately without requiring too much time or toner, with consideration given to the difference in the rotation speed of the intermediary transfer belt 41 depending on whether the secondary transfer roller 42 is contacted with or released from the intermediary transfer belt 41.