In an oil pan, an outer surface of an oil pan body is covered with urethane foam material. The outer surface of the oil pan body is cation treated to be a surface-treated layer, and the urethane foam material is adhered to the outer surface of the oil pan body by the surface-treated layer without any gaps therebetween. The oil pan further includes an undulating portion formed on the outer surface of the oil pan body and undulating in an inward and outward direction. The surface-treated layer is formed on the undulating portion and the urethane foam material is adhered to the undulating portion without any gaps therebetween. The undulating portion includes a bowl-shaped recess recessed into a bowl shape toward an inner side of the oil pan body and the urethane foam material is adhered to an entire inner surface of the bowl-shaped recess without any gaps therebetween.