Position detection device

A position detection device comprising:

• a detector which outputs a count value corresponding to a position of a detection target, and repeating values from zero until an upper limit value;
• an extended data storage unit which stores extended data corresponding to an integrated value of change amount in the count value by the rollover, in a case of there being rollover of the count value transitioning between zero and the upper limit value;
• a position calculation unit which calculates an absolute position of the detection target by adding the count value outputted by the detector and the integrated value indicated by the extended data;
• a section storage unit which, among count sections defined by dividing the range of the count value into at least three, stores the count section in which the count value received from the detector is included;
• and
• a confirmation processing unit which confirms appropriateness of the extended data when position detection processing start, based on an isolation number between the count section stored by the section storage unit, and the count section in which the count value is included after position detection processing start.