A cassette tape player for use with a tape housed in a cassette for recording and/or reproducing the tape. The cassette is generally provided with two capstan insert holes, two guide holes formed between the two capstan insert holes, two pinch roller insert openings respectively contiguous to the two capstan insert holes, two openings respectively contiguous to the two guide holes, and a magnetic head insert opening formed between the two openings. The cassette tape player includes a reversibly rotatable capstan adapted to be inserted into one of the two guide holes; a pinch roller adapted to be inserted through one of the two openings corresponding to the guide hole into which the capstan is to be inserted; a first magnetic head for use in normal running of the tape adapted to be inserted through one of the pinch roller insert openings so that the first magnetic head is located on a supply reel side upstream of the capstan in the normal running; and a second magnetic head for use in reverse running of the tape adapted to be inserted through the magnetic head insert opening so that the second magnetic head is located on a supply reel side upstream of the capstan in the reverse running. Thus, the magnetic head to be used in the recording or reproducing operation is located always on the supply reel side upstream of the capstan.