There is provided an analog-stochastic converter for converting an analog voltage signal into a pulse signal having a corresponding probability. The analog-stochastic converter is implemented using a threshold switching element and a simple logic circuit, thereby reducing a size of the analog-stochastic converter and enabling a low power operation thereof. In addition, in order to update a weight, instead of an analog signal, a probability signal is applied using the above-described analog-stochastic converter, thereby updating a weight in a fully-parallel manner in a synaptic element array having an intersection structure. Accordingly, it is possible to shorten a time for weight update.