A hybrid vehicle comprising: a floor panel including a rising portion that rises upward and extends in a widthwise direction of a vehicle, and a front portion that extends in a forward direction of the vehicle from the rising portion; a fuel tank that is mounted below the floor panel, and that stores liquid fuel burned in an engine serving as a power source of the vehicle; a rear seat provided above the floor panel with a seat portion that supports a hip of a passenger being opposite to the front portion; rear wheel houses arranged at sides of the vehicle in the widthwise direction and at the rear of the rear seat; and left and right side members , which extend in a longitudinal direction of the vehicle, and project upward from each of left and right sides of the front portion so as to support left and right sides of the seat portion of the rear seat with the top surfaces and define side surfaces of a housing space (SP) of a battery in the widthwise direction of the vehicle, wherein the left and right side members define the housing space together with the front portion, the seat portion, and the rising portion, wherein the length of the housing space, defined by the side members, in the widthwise direction of the vehicle is larger than the distance between the rear wheel houses, the hybrid vehicle being characterized in that the length of the housing space, defined by the side members, in the widthwise direction of the vehicle is larger than the distance between the rear wheel houses in order that a first mounting portion and a second mounting portion are formed, the first mounting portion being for mounting a first battery , which stores driving power of an electric motor serving as the power source of the vehicle, and the second mounting portion being formed in the housing space as being side by side with the first mounting portion in the widthwise direction of the vehicle, for mounting a second battery , which assists a power supply by the first battery. a floor panel including a rising portion that rises upward and extends in a widthwise direction of a vehicle, and a front portion that extends in a forward direction of the vehicle from the rising portion; a fuel tank that is mounted below the floor panel, and that stores liquid fuel burned in an engine serving as a power source of the vehicle; a rear seat provided above the floor panel with a seat portion that supports a hip of a passenger being opposite to the front portion; rear wheel houses arranged at sides of the vehicle in the widthwise direction and at the rear of the rear seat; and left and right side members , which extend in a longitudinal direction of the vehicle, and project upward from each of left and right sides of the front portion so as to support left and right sides of the seat portion of the rear seat with the top surfaces and define side surfaces of a housing space (SP) of a battery in the widthwise direction of the vehicle, wherein the left and right side members define the housing space together with the front portion, the seat portion, and the rising portion, wherein the length of the housing space, defined by the side members, in the widthwise direction of the vehicle is larger than the distance between the rear wheel houses, the hybrid vehicle being characterized in that the length of the housing space, defined by the side members, in the widthwise direction of the vehicle is larger than the distance between the rear wheel houses in order that a first mounting portion and a second mounting portion are formed, the first mounting portion being for mounting a first battery , which stores driving power of an electric motor serving as the power source of the vehicle, and the second mounting portion being formed in the housing space as being side by side with the first mounting portion in the widthwise direction of the vehicle, for mounting a second battery , which assists a power supply by the first battery. <EOS>