A magnetic tape recording/reproducing apparatus has a capstan tilt adjustment mechanism for adjusting the tilt of the capstan so that a magnetic tape runs substantially smoothly and without damage to the edges of the tape. The capstan tilt adjustment mechanism has a support plate for pivotally supporting the capstan, first and second supporting parts positioned on both sides of the capstan and which pivotally support the support plate with respect to a chassis, and an adjusting screw mechanism for pivoting the support plate with respect to the chassis. The first and second supporting parts are composed of a wedge-like supporting base portion formed on the chassis and a countersunk screw that passes through a hole in the support plate and screws into the supporting base portion. The supporting base portion has a rigidity that prevents movement of the support plate in a direction perpendicular to this surface. By manipulating the adjusting screw mechanism the support plate is tilted while being supported by the wedge-shaped supporting base portion.