Proposed cooling solution on basis of original vapor chamber with plate-fin heat sink is a promising method of solving the heat dissipation problem in high-power electronic devices. CFD simulation of plate-fin heat sink to predict thermal characteristics of different types of plate-cut finning under two ways of heat input to plate-fin heat sink base (direct input and through a top vapor chamber surface as the heat sink base) was performed. It was found that the heat dissipated by the heat sink with plate-cut finning is 82% of required direct heat input. For the heat sink having plate-cut finning with turn of the cut part of finning, the dissipated heat is about 90% at direct heat input from the heat release source and is more than 99% in case of using the top vapor chamber surface as the heat sink base. The fabrication of thin vapor chamber was done for simulation verification. 75 \(\times \) 75 \(\times \) 0.81 mm \(^3\) vapor chamber (working fluid—water, case—copper, wick (70 \(\,\times \,\) 70 \(\,\times \,\) 0.05 mm \(^3\) )—pillars) was developed and tested. Thermal resistance was 0.13 K/W. The temperature uniformity of vapor chamber was 1.4 \(^\circ \) C. Maximum heat transfer capacity was 45.5 W. Vapor chamber had good temperature uniformity. Verification confirmed the legitimacy of using the approach for simulation of convective heat transfer of the heat sink.