A medium conveying apparatus includes a conveyance roller to convey a medium, a motor to drive the conveyance roller, a signal generator to output a pulse signal, a pulse width of which changes according to a rotation speed of the motor, and a processor to rotate the conveyance roller by controlling the motor, and detect a fluctuation of the pulse width caused by a load fluctuation when the conveyance roller conveys a medium to determine a thickness of the medium according to the pulse width.