a cassette type recording and / or reproducing apparatus having a chassis in which a cassette is mounted on an upper surface thereof . an upper surface of the chassis is formed with a recess in whcih a pair of reels and a gear machanism including a plurality of gears to actuate the pair of reels to rotate are mounted from an above direction , thus reducing a height dimension of the entire apparatus and achieving an easy assembly operation with fewer parts and less labor time for the assembly of the apparatus .