We describe an all-electrical plasmon detection based on the near field coupling between plasmons and percolating electrons. It is the technique to electrically detect the local field enhancement from randomly distributed Cu nanoparticles coupled to a plasmon resonance. In addition, we revealed that plasmon-sensitivity is maximized at the percolation threshold, the minimum Cu particle surface coverage which can make the percolation path through the particles. Our detectors have a simple structure for easy fabrication and a high level of sensitivity to plasmon resonance.