1. A synapse element implementing a function of a synapse composing a neuron of an element of a neural network, comprising: an MOS transistor connected between an internal node and a first voltage and capable of modulating a gain coefficient in analog manner in accordance with a potential of a control gate; wherein said MOS transistor receives at its gate an output signal of another said neuron, potential of said control gate corresponding to a synapse load value, and source-drain current of said MOS transistor represents an output signal of said synapse element.