A starting power generation apparatus (100, 100a, 100b) comprising: a starter generator including a field portion having a permanent magnet, and an armature unit including a first multi-phase winding and a second multi-phase winding which are arranged in parallel; a first power conversion unit including a first positive-side DC terminal connected to a battery and a plurality of first AC terminals connected to the first multi-phase winding, the first power conversion unit being configured to convert a power bidirectionally between DC and AC; a second power conversion unit including a plurality of second AC terminals connected to the second multi-phase winding, the second power conversion unit being configured to control a current to be input and output via the second AC terminals; and a control unit configured to detect a positional relationship between the field portion and the armature unit based on an output voltage of the second multi-phase winding, and control the first power conversion unit and the second power conversion unit in accordance with the positional relationship detected, wherein the control unit is configured to detect the positional relationship when the starter generator is stopped, based on time widths of two or more predetermined voltages generated in two or more windings constituting the second multi-phase winding in a case that an output voltage of the battery is applied to the first multi-phase winding for a predetermined time in a state where current input and output via the second AC terminals is off. a starter generator including a field portion having a permanent magnet, and an armature unit including a first multi-phase winding and a second multi-phase winding which are arranged in parallel; a field portion having a permanent magnet, and an armature unit including a first multi-phase winding and a second multi-phase winding which are arranged in parallel; a first power conversion unit including a first positive-side DC terminal connected to a battery and a plurality of first AC terminals connected to the first multi-phase winding, the first power conversion unit being configured to convert a power bidirectionally between DC and AC; a second power conversion unit including a plurality of second AC terminals connected to the second multi-phase winding, the second power conversion unit being configured to control a current to be input and output via the second AC terminals; and a control unit configured to detect a positional relationship between the field portion and the armature unit based on an output voltage of the second multi-phase winding, and control the first power conversion unit and the second power conversion unit in accordance with the positional relationship detected, detect a positional relationship between the field portion and the armature unit based on an output voltage of the second multi-phase winding, and control the first power conversion unit and the second power conversion unit in accordance with the positional relationship detected, wherein the control unit is configured to detect the positional relationship when the starter generator is stopped, based on time widths of two or more predetermined voltages generated in two or more windings constituting the second multi-phase winding in a case that an output voltage of the battery is applied to the first multi-phase winding for a predetermined time in a state where current input and output via the second AC terminals is off.