The tunneling spectrum of an electron and a hole in metal–superconductor–metal junctions is computed using the Blonder–Tinkham–Klapwijk method. The incident and the outgoing currents finally balance each other by an interface charge inside the superconductor and metal junction. The present computation shows a more abundant structure compared to that on a metal–superconductor junction, such as the resonance at bias voltages above the energy gap of the superconductor. The density of the interface charge shows a quantum-like oscillation.