A cell observation device is cell observation device for observing a cell held by a microplate having a well holding a sample including the cell and includes a microplate holder for holding the microplate thereon, an electrical stimulation unit including an electrode pair including a first electrode and a second electrode, and a position controller for controlling a position of the electrical stimulation unit in a state in which the first electrode is disposed closer to the center of the well than the second electrode when the electrode pair is disposed in the well of the microplate. The tip of the first electrode extends more than the tip of the second electrode.