To shorten the length of a lead, alleviate physical burden on a patient in installation of a device into a body, and miniaturize the device while allowing both treatment based on cardiac stimulation and nerve stimulation. Provided is a nerve stimulation device implanted in the body together with a cardiac treatment device supplying an electric pulse to a heart depending on a cardiac rate, including a stimulation signal outputting part that stimulates a vagus nerve via a stimulation electrode disposed on the vagus nerve, an electric signal detecting part that detects an electric signal transmitted through a tissue outside the heart by a detection electrode disposed on the tissue, a cardiac event determining part that determines a cardiac event containing the electric pulse supplied to the heart by the cardiac treatment device based on the electric signal detected by the electric signal detecting part, and a controlling part that controls the stimulation signal outputting part based on the cardiac event determined by the cardiac event determining part.