In a seek control device based on a current observer control which performs two degree of freedom control, a current step difference to be generated when seek control is switched to following control is prevented. When seek control is switched to following control, a current step difference cancellation trajectory generation section calculates a current value Udiff for the amount of the step difference based on a difference between current values u(n) and u(n-1), and supplies a target position trajectory r'(n) (or target current trajectory) for offsetting this calculated value to a following controller. Therefore the current step difference of the output current is cancelled.