An apparatus for measuring a thickness of a unit cell, the apparatus comprising: a plurality of transfer rollers configured to sequentially transfer unit cells and disposed to be spaced a predetermined distance from each other so that the vertical movement of the unit cells is suppressed while moving; and a thickness sensor disposed at a fixed position to irradiate light to a moving path of "the unit cells and calculate a time when receiving the reflected light, thereby measuring a thickness of each of the unit cells, wherein the thickness sensor comprises: an upper thickness sensor disposed above the transfer rollers to irradiate the light onto a top surface of the unit cell passing between the transfer rollers and calculate a time when receiving the reflected light, thereby measuring a distance from the unit cell; a lower thickness sensor disposed below the transfer rollers to irradiate the light onto a bottom surface of the unit cell between the transfer rollers that are adjacent to each other and calculate a time when receiving the reflected light, thereby measuring a distance from the unit cell; wherein the upper and the lower thickness sensors (40, 50) are disposed at one point between the transfer rollers; and a controller configured to receive a value measured by the upper thickness sensor and a value measured by the lower thickness sensor to calculate the thickness of the unit cell. a plurality of transfer rollers configured to sequentially transfer unit cells and disposed to be spaced a predetermined distance from each other so that the vertical movement of the unit cells is suppressed while moving; and a thickness sensor disposed at a fixed position to irradiate light to a moving path of "the unit cells and calculate a time when receiving the reflected light, thereby measuring a thickness of each of the unit cells, wherein the thickness sensor comprises: an upper thickness sensor disposed above the transfer rollers to irradiate the light onto a top surface of the unit cell passing between the transfer rollers and calculate a time when receiving the reflected light, thereby measuring a distance from the unit cell; a lower thickness sensor disposed below the transfer rollers to irradiate the light onto a bottom surface of the unit cell between the transfer rollers that are adjacent to each other and calculate a time when receiving the reflected light, thereby measuring a distance from the unit cell; wherein the upper and the lower thickness sensors (40, 50) are disposed at one point between the transfer rollers; and a controller configured to receive a value measured by the upper thickness sensor and a value measured by the lower thickness sensor to calculate the thickness of the unit cell. an upper thickness sensor disposed above the transfer rollers to irradiate the light onto a top surface of the unit cell passing between the transfer rollers and calculate a time when receiving the reflected light, thereby measuring a distance from the unit cell; a lower thickness sensor disposed below the transfer rollers to irradiate the light onto a bottom surface of the unit cell between the transfer rollers that are adjacent to each other and calculate a time when receiving the reflected light, thereby measuring a distance from the unit cell; wherein the upper and the lower thickness sensors (40, 50) are disposed at one point between the transfer rollers; and a controller configured to receive a value measured by the upper thickness sensor and a value measured by the lower thickness sensor to calculate the thickness of the unit cell.