Liquid-cooled power unit of a power electronics device, which power unit includes at least two power modules, the cooling surface of which power modules is provided with pin-type protrusions and which power modules are fixed to the frame part of the power unit. A liquid duct is arranged inside the frame part of the power unit, and the power modules are fixed to the points of the apertures situated in the frame part on both sides of the liquid duct in such a way that the pin-type protrusions of the power modules are situated in the liquid duct. A wedge-shaped part is disposed in the liquid duct, which wedge-shaped part includes a wedge-shaped front part for spreading the liquid flow into two essentially equal flows at the point of the power modules.