A securing member for attaching a wall material to a building frame of a building, comprising: a substrate portion ; a bulging portion that bulges from the substrate portion in a direction from a rear surface to a front surface of the substrate portion and extends in a longitudinal direction; a locking portion that extends in the longitudinal direction of the securing member and protrudes from the bulging portion in a direction from the rear surface to the front surface of the substrate portion ; an end-side fixing portion that is provided on the substrate portion at a position biased toward one end from the center of the locking portion in the longitudinal direction, and in which at least both sides in the longitudinal direction and the locking portion side are surrounded by the bulging portion ; characterised by an inner-side bulging portion that forms a portion of the bulging portion adjacent the end-side fixing portion and that includes an inner-side contact surface for coming into contact with a rear surface of the wall material , and is located on a side toward the center of the locking portion in the longitudinal direction with respect to the end-side fixing portion ; and an end-side bulging portion that forms a portion of the bulging portion adjacent the end-side fixing portion and that includes an end-side contact surface for coming into contact with a rear surface of the wall material , and is located on a side opposite to the inner-side bulging portion in the longitudinal direction with respect to the end-side fixing portion , wherein a width in the longitudinal direction of the inner-side contact surface is greater than a width in the longitudinal direction of the end-side contact surface . a substrate portion ; a bulging portion that bulges from the substrate portion in a direction from a rear surface to a front surface of the substrate portion and extends in a longitudinal direction; a locking portion that extends in the longitudinal direction of the securing member and protrudes from the bulging portion in a direction from the rear surface to the front surface of the substrate portion ; an end-side fixing portion that is provided on the substrate portion at a position biased toward one end from the center of the locking portion in the longitudinal direction, and in which at least both sides in the longitudinal direction and the locking portion side are surrounded by the bulging portion ; characterised by an inner-side bulging portion that forms a portion of the bulging portion adjacent the end-side fixing portion and that includes an inner-side contact surface for coming into contact with a rear surface of the wall material , and is located on a side toward the center of the locking portion in the longitudinal direction with respect to the end-side fixing portion ; and an end-side bulging portion that forms a portion of the bulging portion adjacent the end-side fixing portion and that includes an end-side contact surface for coming into contact with a rear surface of the wall material , and is located on a side opposite to the inner-side bulging portion in the longitudinal direction with respect to the end-side fixing portion , wherein a width in the longitudinal direction of the inner-side contact surface is greater than a width in the longitudinal direction of the end-side contact surface . <EOS>