A compression member is used to press a first outer surface of a negative pressure generating member which contacts a surface of a partition wall and to press a second outer surface of the negative pressure generating member which contacts an inner surface of a first recessed portion located opposite the partition wall. The negative pressure generating member is placed in the first recessed portion with releasing the pressure exerted on the first outer surface while maintaining the pressure exerted on the second outer surface. After the negative pressure generating member is placed in the first recessed portion, the pressure exerted on the outer surface of the negative pressure generating member is released.