A device for measuring blood pressure and for indicating the presence of atrial fibrillation, includes an inflatable cuff, a pump, at least one pressure sensor for measuring the pressure inside the cuff, a pressure relief valve for deflating the cuff, and a control unit for controlling the pump and the valve. A calculating unit determines the presence or absence of atrial fibrillation on the basis of pressure variation sensed by the sensor. The calculating unit is adapted to independently determine the presence of atrial fibrillation on the basis of at least one, preferably two sequences, of pulse beats. The control unit is configured to maintain the pressure in a predefined range or to restore the pressure to a predefined range for an additional sequence, and to determine the presence of atrial fibrillation only if the calculating unit determines the presence of atrial fibrillation during a first and/or preceding sequence.