An electricity generation device provided with a permanent-magnet electric generator including three or more phase windings (L1, L2, L3) each having one end serving as an output terminal and the other end connected to a neutral point, characterized by comprising: bidirectional semiconductor switching circuits (TR1, TR2, TR3) connected between the respective phase windings (L1, L2, L3) of the permanent-magnet electric generator and the neutral point and capable of interrupting connections between the respective phase windings (L1, L2, L3) and the neutral point, each of the bidirectional semiconductor switching circuits (TR1, TR2, TR3) allowing electric current to flow therethrough in both directions in a conduction state and, after being input with a gate signal, retaining the conduction state by itself until the electric current stops flowing therethrough; a self-excited gate signal generation circuit configured to generate a gate signal for each of the bidirectional semiconductor switching circuits (TR1, TR2, TR3) associated with the respective phase windings (L1, L2, L3) of the permanent-magnet electric generator from alternating-current voltages excited in those of the phase windings (L1, L2, L3) which are associated with others of the bidirectional semiconductor switching circuits (TR1, TR2, TR3) in such a manner that the gate signal is output to one of the bidirectional semiconductor switching circuits (TR1, TR2, TR3) during a period including a time at which the alternating-current voltage excited in a corresponding one of the phase windings turns from positive to negative and during a period including a time at which the alternating-current voltage excited in the corresponding one of the phase windings turns from negative to positive; and a startup gate signal output circuit configured to output a startup gate signal to all of the bidirectional semiconductor switching circuits (TR1, TR2, TR3) when the permanent-magnet electric generator is to be started. bidirectional semiconductor switching circuits (TR1, TR2, TR3) connected between the respective phase windings (L1, L2, L3) of the permanent-magnet electric generator and the neutral point and capable of interrupting connections between the respective phase windings (L1, L2, L3) and the neutral point, each of the bidirectional semiconductor switching circuits (TR1, TR2, TR3) allowing electric current to flow therethrough in both directions in a conduction state and, after being input with a gate signal, retaining the conduction state by itself until the electric current stops flowing therethrough; a self-excited gate signal generation circuit configured to generate a gate signal for each of the bidirectional semiconductor switching circuits (TR1, TR2, TR3) associated with the respective phase windings (L1, L2, L3) of the permanent-magnet electric generator from alternating-current voltages excited in those of the phase windings (L1, L2, L3) which are associated with others of the bidirectional semiconductor switching circuits (TR1, TR2, TR3) in such a manner that the gate signal is output to one of the bidirectional semiconductor switching circuits (TR1, TR2, TR3) during a period including a time at which the alternating-current voltage excited in a corresponding one of the phase windings turns from positive to negative and during a period including a time at which the alternating-current voltage excited in the corresponding one of the phase windings turns from negative to positive; and a startup gate signal output circuit configured to output a startup gate signal to all of the bidirectional semiconductor switching circuits (TR1, TR2, TR3) when the permanent-magnet electric generator is to be started.