The present invention provides a positioning control device and a disk device for shortening a calculation delay time. Upon detection of a position signal from a demodulation circuit, an MCU of the disk device calculates a position error, and following calculation of a control amount, executes determination and correction processing. A variable value prior to the start of calculation is stored in a save area of a memory (or a save memory) such that when the variable value is to be reset as a result of the determination and correction processing, the variable value is read from the save area, the reset variable value is stored in an overwrite area of the memory (or an overwrite memory), and calculation of the control amount is re-executed.