At the time of forming a paste layer on a substrate sheet by use of three rolls placed at right angles, in order to offset a variation amount of a first gap due to thermal expansion of the rolls, a variation amount in a given detection period is calculated by use of outputs of a first sensor configured to detect a coating film surface of a second-roll coating film of a second roll and a second sensor configured to detect a second-roll surface, and the first roll is moved by use of a first-roll moving mechanism.