A wrinkle smoothing device for a composite body of a continuous sheet related to an absorbent article includes a first belt that moves along a first travel path while retaining the central portion of the continuous sheet, and second and third belts that move along second and third travel paths while retaining side portions of the continuous sheet. The second and third travel path are inclined from the first travel path such that a downstream side is more spaced apart from the first travel path than an upstream side. The second and third belts retain side portions of the continuous sheet while relatively sliding in the width direction of the continuous sheet.