A thin notebook computer mechanical keyboard includes a reinforcement iron plate, a scissor structure, a keycap, a base, a pressing stopper, a spring and a cover. The scissor structure includes first positioning parts vertically and movably clamped on clamping parts of the reinforcement iron plate, and second positioning parts. The keycap includes fastening parts fastened on the second positioning parts. When the keycap is pressed to a certain extent, an action between a hand touch and a fourth terminal produces a sound of an upward impact against the cover. When the keycap is pressed, the scissor structure maintains balance of the whole keycap without catching the keycap, which ensures a favorable touch feeling. A switch can be directly installed on a printed circuit board and pass through the reinforcement iron plate. The scissor structure maintains balance of the keycap, and balanced movement is achieved without falling short of thinning requirements.