A manufacturing method of a composite sheet includes: bonding a belt member to a sheet surface of the belt-like sheet by supplying a belt-like sheet to an outer circumferential surface of a bonding roll; supplying the belt member to a part of the belt-like sheet that is brought in contact with the outer circumferential surface of the bonding roll and overlapping the belt member to the part. The guide member has a reciprocating roller and a supply roller. The method further includes wrapping the belt member subsequently around the outer circumferential surface of the supply roller and the outer circumferential surface of the reciprocating roller, and leading the belt member to the belt-like sheet; and oscillating the supply roller so that the outer circumferential surface of the supply roller faces toward the reciprocating roller in accordance with a reciprocating motion of the reciprocating roller.