An electrode position detection device detects a relative positional relationship between a positive electrode and a negative electrode, when a packaged electrode having the positive electrode disposed inside a bag-shaped separator and the negative electrode are alternately stacked. The device includes a light source, a camera, and a detector. The light source projects light that penetrates the separator and is reflected by the electrodes. The camera receives the light reflected by the positive electrode when the packaged positive electrode is on the uppermost layer and receives the light reflected by the negative electrode when the negative electrode is on the uppermost layer. The detector detects the relative positional relationship between the electrodes based on the results of light reception by the camera when the packaged positive electrode is on the uppermost layer and the results of light reception by the camera when the negative electrode is on the uppermost layer.