Provided is a thin-film magnetic head in which the magnetic spacing can be appropriately controlled by dynamically and accordingly, by adjusting the pressure working between the thin-film magnetic head and the magnetic recording medium according to the change of conditions such as the change over time. The thin-film magnetic head comprises at least one cavity for adjusting a pressure working between the thin-film magnetic head and the magnetic recording medium, provided in a surface of the head opposed to the magnetic recording medium, and a volume of the at least one cavity being variable. When the magnetic recording medium passes through near the cavity, the cavity generates a (negative) pressure that attracts the head and the medium toward each other. The amount of the negative pressure depends on the volume of the cavity; thus, a magnetic spacing dMS can be controlled dynamically and accordingly by adjusting the volume.