A field winding rotating electrical machine includes a field current detection section, a field current control section configured to calculate a duty ratio of a current supplied to the field winding based on a field current detection value, to thereby control current supply to the field winding by using a switching element, and a field current correction section configured to estimate a time point when the field current becomes 0 A based on a control state of the field current, to specify the field current detection value at the estimated time point to be a field current correction value, and to subtract the field current correction value from the field current detection value, to thereby calculate the corrected field current value. The field current control section controls the current supply based on the corrected field current value calculated by the field current correction section.