A magnetic recording/reproducing apparatus is disclosed that is arranged to receive a tape cassette accommodating a tape recording medium that is selectively loaded thereto. The apparatus includes a rotating drum unit having a rotating head, and a loading mechanism that is configured to pull the tape recording medium of the loaded tape cassette out of the loaded tape cassette, wind the tape recording medium around the rotating drum unit, and form a tape path. The loading mechanism includes a short loading pole that is adapted for a first tape cassette accommodating a narrow tape recording medium and a long loading pole that is adapted for a second tape cassette accommodating a wide tape recording medium, which short pole and long pole are positioned at the same height, and a loading pole raising mechanism that is configured to raise the long loading pole when the second tape cassette is loaded.