Provided is a magnetic sensor device capable of attenuating the intensity of the magnetic field to be applied to the magnetic sensor. A magnetic sensor device includes a magnetic sensor element which detects the intensity of a magnetic field in a predetermined detection axis direction, and a magnetic field attenuation body which includes a first magnetic field attenuation unit and a second magnetic field attenuation unit, each of the attenuation units having a surface and the surfaces being opposed to each other with the magnetic sensor element therebetween.