A blood pressure monitor is provided with a box-shaped housing having openings formed in left and right side walls, a cuff transversely arranged in the housing and including an arm entrance and an arm exit at the opposite left and right ends corresponding to the openings. The cuff is formed with a blood flow blocking bag in a specified area. The opposite ends of the cuff is taken up by a cuff take-up drum such that the blood flow blocking bag extends along the outer circumferential surface of the inserted arm at the time of a measurement and a compressed air is supplied to the blood flow blocking bag to block the blood flow. The blood pressure monitor is further provided with at least one of a fastening force adjusting construction for adjusting a force of the cuff to evenly fasten the arm or the like of the measurer, a construction for preventing the epidermis part of the arm from getting in the cuff, a construction for suppressing the consumption of an electric power, and a construction for fixing a measuring position.