A method for manufacturing an absorbent article including a front waistline portion to be fitted to a front waistline of a wearer, a back waistline portion to be fitted to a back waistline of the wearer, and a crotch portion to be fitted to a crotch of the wearer, the crotch portion arranged between the front waistline portion and the back waistline portion, the method comprising: a web conveying step of conveying a strip-shaped front waistline web to be formed into the front waistline portion and a strip-shaped back waistline web to be formed into the back waistline portion by a web conveying mechanism with the webs being arranged side by side in a width direction of the webs; a flap attaching step of attaching a flap portion onto a waistline portion of either the front waistline web or the back waistline web, the flap portion fixed to either the front waistline portion or the back waistline portion being temporarily attached to the other waistline portion when being worn; a web gap changing step of changing a gap between the front waistline web and the back waistline web by a web gap changing mechanism; a crotch member attaching step of attaching a crotch member to be formed into the crotch portion to a portion between the front waistline web and the back waistline web, wherein the web gap changing step is performed between the flap attaching step and the crotch member attaching step; and wherein the web gap changing mechanism includes: a pair of first web guiding portions arranged in the web conveyance direction; and at least one second web guiding portion arranged between the pair of first web guiding portions on a conveyance path of at least one of the webs, in a view in a cross direction which is a direction perpendicular to the web conveyance direction and is a direction along a surface of the web, the second web guiding portion is arranged at a position to form a step in the web being conveyed, in the plan view of the web, a first contact line and a second contact line run in the cross direction, the first contact line running along a first contact surface on which one of the first web guiding portions and the web come into contact with each other, the second contact line running along a second contact surface on which the other first web guiding portion and the web come into contact with each other, in the plan view of the web, a third contact line is inclined with respect to the first contact line and the second contact line, the third contact line running along a third contact surface on which the second web guiding portion and the web come into contact with each other, and the web gap changing mechanism is used for at least any one of the front waistline web and the back waistline web. a web conveying step of conveying a strip-shaped front waistline web to be formed into the front waistline portion and a strip-shaped back waistline web to be formed into the back waistline portion by a web conveying mechanism with the webs being arranged side by side in a width direction of the webs; a flap attaching step of attaching a flap portion onto a waistline portion of either the front waistline web or the back waistline web, the flap portion fixed to either the front waistline portion or the back waistline portion being temporarily attached to the other waistline portion when being worn; a web gap changing step of changing a gap between the front waistline web and the back waistline web by a web gap changing mechanism; a crotch member attaching step of attaching a crotch member to be formed into the crotch portion to a portion between the front waistline web and the back waistline web, wherein the web gap changing step is performed between the flap attaching step and the crotch member attaching step; and wherein the web gap changing mechanism includes: a pair of first web guiding portions arranged in the web conveyance direction; and at least one second web guiding portion arranged between the pair of first web guiding portions on a conveyance path of at least one of the webs, a pair of first web guiding portions arranged in the web conveyance direction; and at least one second web guiding portion arranged between the pair of first web guiding portions on a conveyance path of at least one of the webs, in a view in a cross direction which is a direction perpendicular to the web conveyance direction and is a direction along a surface of the web, the second web guiding portion is arranged at a position to form a step in the web being conveyed, in the plan view of the web, a first contact line and a second contact line run in the cross direction, the first contact line running along a first contact surface on which one of the first web guiding portions and the web come into contact with each other, the second contact line running along a second contact surface on which the other first web guiding portion and the web come into contact with each other, in the plan view of the web, a third contact line is inclined with respect to the first contact line and the second contact line, the third contact line running along a third contact surface on which the second web guiding portion and the web come into contact with each other, and the web gap changing mechanism is used for at least any one of the front waistline web and the back waistline web.