In a magnetic tape magazine of small size containing a thin tape for long play, one of a pair of guide walls is provided between a fixed guide pin and a rotatable guide roller on either side of the tape retaining section of the interior space of the magazine. The guide walls are made of non-magnetizable material and have a smooth flat surface to smoothly guide the tape and prevent the tape from winding around the rotatable guide rollers or being distorted while being fed in a recording or reproducing operation. A partition is provided in the tape magazine to divide the interior of the magazine into a tape retaining section and a recording and reproducing section. Between both ends of the partition and the rotatable guide rollers are provided additional guide walls.