A driving unit of an image forming apparatus is configured in such a manner that an engagement noise frequency is larger than an image-quality assurance frequency and that the engagement noise frequency is less than or equal to an upper limit frequency of a one-third octave band frequency range including the image-quality assurance frequency. The image-quality assurance frequency is defined as a frequency obtained by multiplying a conveying speed of a recording medium by a value of 1.6, and the engagement noise frequency is defined as a frequency obtained by multiplying a predetermined number of teeth of a first gear by a rotational speed of a motor, when a unit of the conveying speed of the recording medium is millimeters per second, a unit of the value of 1.6 is cycles per millimeter, and a unit of the rotational speed of the motor is revolutions per second.