A product-sum operation device including: product operation units generating output signals by multiplying input signals corresponding to input values; a current detection unit executing a current detecting process in which a current output from the product operation units with a predetermined time delay from input of the input signal and a current output from the product operation units at an interval thereafter are detected in a time span from a first transient response to before occurrence of a second transient response, the first transient response due to charging to a parasitic capacitance of the product operation units by input of the input signal and the second transient response being due to discharging from the parasitic capacitance of the product operation units by input of the input signal; and a sum operation unit calculating a value relating to a total sum of the output signals based on currents detected.