A power conversion device , comprising: a power semiconductor module that converts DC current to AC current; a capacitor that smooths DC power; a first flow conduit defining member that defines a first flow conduit in which coolant flows, and that also defines a first storage space in which the power semiconductor module is housed; and a second flow conduit defining member that defines a second flow conduit in which coolant flows, and that also defines a second storage space in which the capacitor is housed, wherein: when in use the first flow conduit defining member and the second flow conduit defining member are arranged so that, when viewed from above the power conversion device , the first flow conduit for cooling the power semiconductor modules and the second flow conduit for cooling the capacitor are arranged so that they do not overlap in the vertical direction; the first flow conduit defining member is disposed beneath a plane that coincides with a lower surface of the second flow conduit defining member ; and a first space , in which a vehicle component that is different from the power conversion device can be disposed, is defined in a space to a side of the first flow conduit defining member and below the second flow conduit defining member . a power semiconductor module that converts DC current to AC current; a capacitor that smooths DC power; a first flow conduit defining member that defines a first flow conduit in which coolant flows, and that also defines a first storage space in which the power semiconductor module is housed; and a second flow conduit defining member that defines a second flow conduit in which coolant flows, and that also defines a second storage space in which the capacitor is housed, wherein: when in use the first flow conduit defining member and the second flow conduit defining member are arranged so that, when viewed from above the power conversion device , the first flow conduit for cooling the power semiconductor modules and the second flow conduit for cooling the capacitor are arranged so that they do not overlap in the vertical direction; the first flow conduit defining member is disposed beneath a plane that coincides with a lower surface of the second flow conduit defining member ; and a first space , in which a vehicle component that is different from the power conversion device can be disposed, is defined in a space to a side of the first flow conduit defining member and below the second flow conduit defining member . when in use the first flow conduit defining member and the second flow conduit defining member are arranged so that, when viewed from above the power conversion device , the first flow conduit for cooling the power semiconductor modules and the second flow conduit for cooling the capacitor are arranged so that they do not overlap in the vertical direction; the first flow conduit defining member is disposed beneath a plane that coincides with a lower surface of the second flow conduit defining member ; and a first space , in which a vehicle component that is different from the power conversion device can be disposed, is defined in a space to a side of the first flow conduit defining member and below the second flow conduit defining member . <EOS>