A power transmission device comprising: an input shaft configured to input power from a first power source; a second power source; a first output shaft configured to transmit power to first drive wheels; a second output shaft configured to transmit power to second drive wheels; a differential having three rotational elements; and a connection switching device configured to selectively switch a connection relationship among the input shaft, the first output shaft, the second output shaft, and the three rotational elements, wherein the connection switching device is configured to selectively fix any one rotational element among the three rotational elements to a fixing member, the second power source is coupled to one of the rotational elements other than the rotational element fixed by the connection switching device to the fixing member among the three rotational elements, the differential is configured to be switched between a plurality of modes by the connection switching device, and the plurality of modes includes a first mode in which any one rotational element among the three rotational elements is fixed to the fixing member, one of the rotational elements other than the rotational element fixed to the fixing member is coupled to the input shaft, and the other of the rotational elements other than the rotational element fixed to the fixing member is coupled to the first output shaft, characterized in that the plurality of modes includes: a second mode in which the three rotational elements are respectively coupled to the second power source, the first output shaft, and the second output shaft. an input shaft configured to input power from a first power source; a second power source; a first output shaft configured to transmit power to first drive wheels; a second output shaft configured to transmit power to second drive wheels; a differential having three rotational elements; and a connection switching device configured to selectively switch a connection relationship among the input shaft, the first output shaft, the second output shaft, and the three rotational elements, wherein the connection switching device is configured to selectively fix any one rotational element among the three rotational elements to a fixing member, the second power source is coupled to one of the rotational elements other than the rotational element fixed by the connection switching device to the fixing member among the three rotational elements, the differential is configured to be switched between a plurality of modes by the connection switching device, and the plurality of modes includes a first mode in which any one rotational element among the three rotational elements is fixed to the fixing member, one of the rotational elements other than the rotational element fixed to the fixing member is coupled to the input shaft, and the other of the rotational elements other than the rotational element fixed to the fixing member is coupled to the first output shaft, characterized in that the plurality of modes includes: a second mode in which the three rotational elements are respectively coupled to the second power source, the first output shaft, and the second output shaft.