An image forming apparatus that conveys a sheet and prints an image on the sheet, includes: a sheet feed tray on which the sheet is placed; a motor that drivingly rotates a polygon mirror with which a latent image corresponding to the image is formed; a hardware processor that identifies a type of the sheet based on an output from a sensor provided between the sheet feed tray and a position at which the printing takes place, on a conveyance path for the sheet; and a motor controller that changes a rotation speed of the motor to a first speed, starting from a startup timing synchronized with starting of conveyance of the sheet, wherein the startup timing is set in such a manner that an identification timing at which the type of the sheet is identified arrives while the changing to the first speed is still in progress.