A magnetic recording/reproducing device of the present invention records information on or reproduces information from a tape provided in a cassette by winding the tape around a rotary head cylinder at a prescribed angle after the tape is drawn out from the cassette including a supply reel and a take-up reel by tape guide members. The device is characterized in that: a first tape guide member is located downstream in the tape running direction with respect to the supply reel; the first tape guide member is followed by a second tape guide member, a third tape guide member and the rotary head cylinder; and only the first tape guide member, the second tape guide member and the third tape guide member are provided between the supply reel and the rotary head cylinder.