A work vehicle comprising: a power unit (B); an electric motor (M) activated by electric power from the power unit (B); a propelling transmission system for receiving drive power from the electric motor (M); a cabin (D) in which the driver rides, the cabin (D) including a roof portion (R); and an air conditioner (S) for adjusting air temperature in the interior of the cabin (D), the power unit (B) and the air conditioner (S) being provided in the roof portion (R) of the cabin (D); characterized in that the roof portion (R) includes a bottom wall provided in the interior of the cabin (D) and serving as a ceiling wall of the cabin (D), an upper wall provided above the bottom wall , and an exterior wall above the upper wall ; a roof interior space (K) is defined between the bottom wall and the upper wall for housing the power unit (B), and a ventilation space (T) is defined between the upper wall and the exterior wall for taking in air from the outside of the cabin (D) to be separated from a cooling space (N) in the roof portion (R); and that air taken in from the ventilation space (T) is supplied to the air conditioner (S) when the air conditioner (S) performs ventilation in the interior of the cabin (D), wherein a unit housing case for housing the power unit (B), an air-intake duct for supplying air from the outside of the cabin (D) to the unit housing case , and an air-discharge duct for feeding out air within the unit housing case to the outside of the cabin (D) are provided in the roof interior space (K), that the cooling space (N) is formed from an interior space of the air-intake duct , an interior space of the unit housing case and an interior space of the air-discharge duct , that air is drawn from the outside of the cabin (D) through the air-intake duct , and that a fan is provided in the cooling space (N) for discharging air from the unit housing case to the outside of the cabin (D) through the air-discharge duct . a power unit (B); an electric motor (M) activated by electric power from the power unit (B); a propelling transmission system for receiving drive power from the electric motor (M); a cabin (D) in which the driver rides, the cabin (D) including a roof portion (R); and an air conditioner (S) for adjusting air temperature in the interior of the cabin (D), the power unit (B) and the air conditioner (S) being provided in the roof portion (R) of the cabin (D); characterized in that the roof portion (R) includes a bottom wall provided in the interior of the cabin (D) and serving as a ceiling wall of the cabin (D), an upper wall provided above the bottom wall , and an exterior wall above the upper wall ; a roof interior space (K) is defined between the bottom wall and the upper wall for housing the power unit (B), and a ventilation space (T) is defined between the upper wall and the exterior wall for taking in air from the outside of the cabin (D) to be separated from a cooling space (N) in the roof portion (R); and that air taken in from the ventilation space (T) is supplied to the air conditioner (S) when the air conditioner (S) performs ventilation in the interior of the cabin (D), wherein a unit housing case for housing the power unit (B), an air-intake duct for supplying air from the outside of the cabin (D) to the unit housing case , and an air-discharge duct for feeding out air within the unit housing case to the outside of the cabin (D) are provided in the roof interior space (K), that the cooling space (N) is formed from an interior space of the air-intake duct , an interior space of the unit housing case and an interior space of the air-discharge duct , that air is drawn from the outside of the cabin (D) through the air-intake duct , and that a fan is provided in the cooling space (N) for discharging air from the unit housing case to the outside of the cabin (D) through the air-discharge duct . <EOS>