A straddle vehicle comprising: an engine that is configured to generate traveling power to be transmitted to a driving wheel; an electric motor that is configured to generate traveling power to be transmitted to the driving wheel; an on-vehicle part disposed behind the engine and including a battery that is configured to store electric power to be supplied to the electric motor; and a traveling wind passage structure disposed at a lateral side of the on-vehicle part, wherein: the battery includes at least one heat radiator exposed on at least one of side surfaces of the battery; the traveling wind passage structure includes at least one inflow port into which traveling wind flows, at least one outflow port from which the traveling wind flows, and at least one side wall that is located between the inflow port and the outflow port and defines a passage between the at least one side wall and a side surface of the on-vehicle part; the passage includes a heat exchange region adjacently located at a lateral side of the heat radiator and an upstream region adjacently located upstream of the heat exchange region; characterized in that the inflow port is open forward and located outside the engine in a vehicle width direction, and in that a dimension in the vehicle width direction of a passage sectional area of the heat exchange region is smaller than a dimension in the vehicle width direction of a passage sectional area of the upstream region. an engine that is configured to generate traveling power to be transmitted to a driving wheel; an electric motor that is configured to generate traveling power to be transmitted to the driving wheel; an on-vehicle part disposed behind the engine and including a battery that is configured to store electric power to be supplied to the electric motor; and a traveling wind passage structure disposed at a lateral side of the on-vehicle part, wherein: the battery includes at least one heat radiator exposed on at least one of side surfaces of the battery; the traveling wind passage structure includes at least one inflow port into which traveling wind flows, at least one outflow port from which the traveling wind flows, and at least one side wall that is located between the inflow port and the outflow port and defines a passage between the at least one side wall and a side surface of the on-vehicle part; the passage includes a heat exchange region adjacently located at a lateral side of the heat radiator and an upstream region adjacently located upstream of the heat exchange region; characterized in that the inflow port is open forward and located outside the engine in a vehicle width direction, and in that a dimension in the vehicle width direction of a passage sectional area of the heat exchange region is smaller than a dimension in the vehicle width direction of a passage sectional area of the upstream region. the battery includes at least one heat radiator exposed on at least one of side surfaces of the battery; the traveling wind passage structure includes at least one inflow port into which traveling wind flows, at least one outflow port from which the traveling wind flows, and at least one side wall that is located between the inflow port and the outflow port and defines a passage between the at least one side wall and a side surface of the on-vehicle part; at least one inflow port into which traveling wind flows, at least one outflow port from which the traveling wind flows, and at least one side wall that is located between the inflow port and the outflow port and defines a passage between the at least one side wall and a side surface of the on-vehicle part; the passage includes a heat exchange region adjacently located at a lateral side of the heat radiator and an upstream region adjacently located upstream of the heat exchange region; a heat exchange region adjacently located at a lateral side of the heat radiator and an upstream region adjacently located upstream of the heat exchange region; characterized in that the inflow port is open forward and located outside the engine in a vehicle width direction, and in that a dimension in the vehicle width direction of a passage sectional area of the heat exchange region is smaller than a dimension in the vehicle width direction of a passage sectional area of the upstream region.