A starting power generation apparatus (100, 100a, 100b, 100c) 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 (61, 61b) including a first positive-side DC terminal connected to a battery, and a plurality of first AC terminals (611, 612, 613) connected to the first multi-phase winding, the first power conversion unit (61, 61b) being configured to convert a power bidirectionally between DC and AC; a second power conversion unit (62, 62b) including a plurality of second AC terminals (621, 622, 623) connected to the second multi-phase winding, the second power conversion unit (62, 62b) being configured to control a current to be input and output via the second AC terminals (621, 622, 623); 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 (61, 61b) and the second power conversion unit (62, 62b) in accordance with the positional relationship detected, wherein the control unit is configured to when an engine is started, energize only the first multi-phase winding according to a plurality of conduction patterns, and compare voltages induced in the second multi-phase winding among the plurality of conduction patterns, thereby detecting the positional relationship, after energization is started, energize the first multi-phase winding and the second multi-phase winding until starting of the engine is completed, based on the positional relationship derived from a zero-cross point of the second multi-phase winding, and after the starting of the engine is completed, de-energize the second multi-phase winding and detect the positional relationship from a zero-cross point of a no-load voltage to be generated at both ends of the second multi-phase winding. 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 (61, 61b) including a first positive-side DC terminal connected to a battery, and a plurality of first AC terminals (611, 612, 613) connected to the first multi-phase winding, the first power conversion unit (61, 61b) being configured to convert a power bidirectionally between DC and AC; a second power conversion unit (62, 62b) including a plurality of second AC terminals (621, 622, 623) connected to the second multi-phase winding, the second power conversion unit (62, 62b) being configured to control a current to be input and output via the second AC terminals (621, 622, 623); 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 (61, 61b) and the second power conversion unit (62, 62b) 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 (61, 61b) and the second power conversion unit (62, 62b) in accordance with the positional relationship detected, wherein the control unit is configured to when an engine is started, energize only the first multi-phase winding according to a plurality of conduction patterns, and compare voltages induced in the second multi-phase winding among the plurality of conduction patterns, thereby detecting the positional relationship, after energization is started, energize the first multi-phase winding and the second multi-phase winding until starting of the engine is completed, based on the positional relationship derived from a zero-cross point of the second multi-phase winding, and after the starting of the engine is completed, de-energize the second multi-phase winding and detect the positional relationship from a zero-cross point of a no-load voltage to be generated at both ends of the second multi-phase winding. when an engine is started, energize only the first multi-phase winding according to a plurality of conduction patterns, and compare voltages induced in the second multi-phase winding among the plurality of conduction patterns, thereby detecting the positional relationship, after energization is started, energize the first multi-phase winding and the second multi-phase winding until starting of the engine is completed, based on the positional relationship derived from a zero-cross point of the second multi-phase winding, and after the starting of the engine is completed, de-energize the second multi-phase winding and detect the positional relationship from a zero-cross point of a no-load voltage to be generated at both ends of the second multi-phase winding.