A cell observation device for observing a cell held by a microplate including a well holding a sample including the cell, the well having a concave bottomed cross-sectional shape in a depth direction, the cell observation device comprising: a mounting unit for holding the microplate; an electrical stimulation device for being inserted into the microplate well applying electrical stimulation to the cell, the electrical stimulation device comprising: an electrode pair including a first electrode and a second electrode, wherein a tip of the first electrode extends in the depth direction of the well more than a tip of the second electrode, and the first electrode is disposed closer to the center of the well of the microplate than the second electrode when the electrode pair is disposed in the well of the microplate; a moving image acquiring unit adapted to detect a two-dimensional optical image of the microplate including light emitted from the sample held in the well and adapted to acquire moving image data representing the two-dimensional optical image; and a position control unit adapted to control a position of the electrode pair in a state in which the first electrode is disposed closer to the center of the well of the microplate than the second electrode when the electrode pair is disposed in the well of the microplate and further adapted to control the tip of the first electrode so as to be located close to the center of a bottom face of the well by inserting the electrode pair into the well such that the tip of the second electrode comes in contact with an outside of the center of the bottom face of the well. a mounting unit for holding the microplate; an electrical stimulation device for being inserted into the microplate well applying electrical stimulation to the cell, the electrical stimulation device comprising: an electrode pair including a first electrode and a second electrode, wherein a tip of the first electrode extends in the depth direction of the well more than a tip of the second electrode, and the first electrode is disposed closer to the center of the well of the microplate than the second electrode when the electrode pair is disposed in the well of the microplate; an electrode pair including a first electrode and a second electrode, wherein a tip of the first electrode extends in the depth direction of the well more than a tip of the second electrode, and the first electrode is disposed closer to the center of the well of the microplate than the second electrode when the electrode pair is disposed in the well of the microplate; a moving image acquiring unit adapted to detect a two-dimensional optical image of the microplate including light emitted from the sample held in the well and adapted to acquire moving image data representing the two-dimensional optical image; and a position control unit adapted to control a position of the electrode pair in a state in which the first electrode is disposed closer to the center of the well of the microplate than the second electrode when the electrode pair is disposed in the well of the microplate and further adapted to control the tip of the first electrode so as to be located close to the center of a bottom face of the well by inserting the electrode pair into the well such that the tip of the second electrode comes in contact with an outside of the center of the bottom face of the well.