A field winding rotating electrical machine, comprising: an armature winding; a field winding; a field current detection section configured to detect a field current flowing in the field winding; 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 detected by the field current detection section, to thereby control current supply to the field winding by using a switching element (63a - 63c, 64a - 64c); characterized by a field current correction section configured to estimate, while the current supply to the field winding is being controlled by the field current control section, 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 detected by the field current detection section at the estimated time point to be a field current correction value, and to subtract the specified field current correction value from the field current detection value detected by the field current detection section, to thereby calculate the corrected field current value, wherein the field current control section is configured to control the current supply based on the corrected field current value calculated by the field current correction section, wherein the field current correction section is configured to estimate a time point when a state where the duty ratio calculated by the field current control section is zero, which corresponds to the control state of the field current, continues for a predetermined time period (Cth) to be the time point when the field current becomes 0 A, and wherein the predetermined time period used by the field current correction section is set to a value based on a time constant of the field winding. an armature winding; a field winding; a field current detection section configured to detect a field current flowing in the field winding; 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 detected by the field current detection section, to thereby control current supply to the field winding by using a switching element (63a - 63c, 64a - 64c); characterized by a field current correction section configured to estimate, while the current supply to the field winding is being controlled by the field current control section, 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 detected by the field current detection section at the estimated time point to be a field current correction value, and to subtract the specified field current correction value from the field current detection value detected by the field current detection section, to thereby calculate the corrected field current value, wherein the field current control section is configured to control the current supply based on the corrected field current value calculated by the field current correction section, wherein the field current correction section is configured to estimate a time point when a state where the duty ratio calculated by the field current control section is zero, which corresponds to the control state of the field current, continues for a predetermined time period (Cth) to be the time point when the field current becomes 0 A, and wherein the predetermined time period used by the field current correction section is set to a value based on a time constant of the field winding.