A magnetic recording and reproduction apparatus includes a main chassis having a rotatable head cylinder provided thereon; and a sub chassis on which a tape cassette is mountable. The sub chassis is movable relative to the main chassis. A pivotable body is provided on the main chassis. The pivotable body has a projection provided thereon. The projection is engaged with a cam groove in the sub chassis so as to pivot the pivotable body. Thus, the cam groove is restricted by the projection, so that the sub chassis moves with respect to the main chassis. The cam groove has a width substantially identical to the diameter of the projection. The cam groove includes first and second arc portions continuous with each other, and a straight portion continuous with the second arc portion. The first and second arc portions have identical radii, and are projected in opposite directions.