PURPOSE: To facilitate size reduction and the increase in density with simple constitution as to an impedance roller holding mechanism by providing a controlled member which turned successively by a tape drawn-out member to a support member, and the 1st and the 2nd exciting means.

CONSTITUTION: The impedance roller holding mechanism 29 consists of the support member 31 which supports freely rotatably an impedance roller 30 for adding equivalent inertial mass to a magnetic tape 27 at its intermediate part, and the controlled member 32 for turn control whose intermediate part is supported freely turnably on the support member 31 through a rotating shaft 311. The support member 31 engages with an engagement part 312 so that a spring member 33 feeds its energizing force to an engagement part 312 formed at one terminal part clockwise in a figure. This saves considerably the space for turning tracks of the support member 31 and controlled member 32, and other components such as a motor 34 are used as auxiliary members.