A magnetic bearing control apparatus , comprising: an electromagnet which supports a control object in a state floating in the air; an inductor connected in series to a coil of the electromagnet ; a switching amplifier which supplies a current to the electromagnet ( ; voltage extracting means which extracts a voltage generated in the inductor at a prescribed timing; sample-holding means which generates the timing and which holds a voltage extracted at the timing; current change rate obtaining means which obtains, based on a voltage held by the sample-holding means, a signal proportional to a time derivative of a current flowing through the coil of the electromagnet ; and displacement estimating means which estimates, based on a signal obtained by the current change rate obtaining means, a displacement between the control object and the electromagnet , wherein a current supplied to the electromagnet is controlled based on a displacement estimated by the displacement estimating means , wherein a displacement detection period for extracting a voltage applied to the inductor is set to a control cycle of the switching amplifier , a current increase period in which a current increases and a current decrease period in which the current decreases are formed in the displacement detection period, the voltage extracting means extracts the voltages applied to the inductor at prescribed timings in each of the current increase period and the current decrease period, subtracting means subtracts one of the extracted voltages from the other, wherein a displacement between the control object and the electromagnet is estimated based on the voltage obtained by the subtraction by the subtracting means , and an adding means adds up two extracted voltages, wherein a current flowing through the electromagnet is estimated based on a value obtained by addition by the adding means . an electromagnet which supports a control object in a state floating in the air; an inductor connected in series to a coil of the electromagnet ; a switching amplifier which supplies a current to the electromagnet ( ; voltage extracting means which extracts a voltage generated in the inductor at a prescribed timing; sample-holding means which generates the timing and which holds a voltage extracted at the timing; current change rate obtaining means which obtains, based on a voltage held by the sample-holding means, a signal proportional to a time derivative of a current flowing through the coil of the electromagnet ; and displacement estimating means which estimates, based on a signal obtained by the current change rate obtaining means, a displacement between the control object and the electromagnet , wherein a current supplied to the electromagnet is controlled based on a displacement estimated by the displacement estimating means , wherein a displacement detection period for extracting a voltage applied to the inductor is set to a control cycle of the switching amplifier , a current increase period in which a current increases and a current decrease period in which the current decreases are formed in the displacement detection period, the voltage extracting means extracts the voltages applied to the inductor at prescribed timings in each of the current increase period and the current decrease period, subtracting means subtracts one of the extracted voltages from the other, wherein a displacement between the control object and the electromagnet is estimated based on the voltage obtained by the subtraction by the subtracting means , and an adding means adds up two extracted voltages, wherein a current flowing through the electromagnet is estimated based on a value obtained by addition by the adding means . <EOS>