A method of smoothing out wrinkles of a composite body of a continuous sheet, in a state a polymeric material is overlapped to a central portion in a width direction of the continuous sheet that travels, to which a depression is shaped at the central portion by a protruding member being pressed against the central portion from the continuous sheet side, the wrinkle smoothing method for a composite body of a continuous sheet related to an absorbent article comprising: i. moving a first belt along a first travel path while making the first belt that is provided along the first travel path retain the central portion of the continuous sheet; ii. moving a second belt along a second travel path while making the second belt that is provided adjacent the first belt on the one side in the width direction thereof retain a portion at one side from the central portion of the continuous sheet; and iii. moving a third belt along a third travel path while making the third belt provided adjacent the first belt on the other side in the width direction thereof retain a portion at an other side from the central portion of the continuous sheet, and, wherein iv. the second travel path is inclined from the first travel path such that a downstream side is more spaced apart from the first travel path to the one side in the width direction, than the upstream side v. the third travel path is inclined from the first travel path such that a downstream side is more spaced apart from the first travel path to the other side in the width direction than the upstream side, vi. the second belt retains a portion on the one side of the continuous sheet while relatively sliding in the width direction of the continuous sheet, and vii. the third belt retains a portion on the other side of the continuous sheet while relatively sliding in the width direction of the continuous sheet. i. moving a first belt along a first travel path while making the first belt that is provided along the first travel path retain the central portion of the continuous sheet; ii. moving a second belt along a second travel path while making the second belt that is provided adjacent the first belt on the one side in the width direction thereof retain a portion at one side from the central portion of the continuous sheet; and iii. moving a third belt along a third travel path while making the third belt provided adjacent the first belt on the other side in the width direction thereof retain a portion at an other side from the central portion of the continuous sheet, and, wherein iv. the second travel path is inclined from the first travel path such that a downstream side is more spaced apart from the first travel path to the one side in the width direction, than the upstream side v. the third travel path is inclined from the first travel path such that a downstream side is more spaced apart from the first travel path to the other side in the width direction than the upstream side, vi. the second belt retains a portion on the one side of the continuous sheet while relatively sliding in the width direction of the continuous sheet, and vii. the third belt retains a portion on the other side of the continuous sheet while relatively sliding in the width direction of the continuous sheet.