A drive control device controls a rotation speed of a rotatable member. A rotation drive member drives the rotatable member. A plurality of objects to be detected are provided in the rotatable member. A detector detects the objects to be detected, which are rotating with rotation of the rotatable member, and outputs a detection signal. A control part detects an angular speed of the rotatable member in accordance with the detection signal, and controls a rotation speed of the rotation drive member. The control part calculates an amount of error in intervals of the objects to be detected, and controls the rotation speed of the rotation drive member in accordance with the amount of error.